Commit Graph

183 Commits

Author SHA1 Message Date
David Howells
4fa7ec5db7 vfs: Convert pipe to use the new mount API
Convert the pipe filesystem to the new internal mount API as the old
one will be obsoleted and removed.  This allows greater flexibility in
communication of mount parameters between userspace, the VFS and the
filesystem.

See Documentation/filesystems/mount_api.txt for more information.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-05-25 18:00:07 -04:00
Al Viro
1f58bb18f6 mount_pseudo(): drop 'name' argument, switch to d_make_root()
Once upon a time we used to set ->d_name of e.g. pipefs root
so that d_path() on pipes would work.  These days it's
completely pointless - dentries of pipes are not even connected
to pipefs root.  However, mount_pseudo() had set the root
dentry name (passed as the second argument) and callers
kept inventing names to pass to it.  Including those that
didn't *have* any non-root dentries to start with...

All of that had been pointless for about 8 years now; it's
time to get rid of that cargo-culting...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-05-25 17:59:24 -04:00
Linus Torvalds
6b3a707736 Merge branch 'page-refs' (page ref overflow)
Merge page ref overflow branch.

Jann Horn reported that he can overflow the page ref count with
sufficient memory (and a filesystem that is intentionally extremely
slow).

Admittedly it's not exactly easy.  To have more than four billion
references to a page requires a minimum of 32GB of kernel memory just
for the pointers to the pages, much less any metadata to keep track of
those pointers.  Jann needed a total of 140GB of memory and a specially
crafted filesystem that leaves all reads pending (in order to not ever
free the page references and just keep adding more).

Still, we have a fairly straightforward way to limit the two obvious
user-controllable sources of page references: direct-IO like page
references gotten through get_user_pages(), and the splice pipe page
duplication.  So let's just do that.

* branch page-refs:
  fs: prevent page refcount overflow in pipe_buf_get
  mm: prevent get_user_pages() from overflowing page refcount
  mm: add 'try_get_page()' helper function
  mm: make page ref count overflow check tighter and more explicit
2019-04-14 15:09:40 -07:00
Matthew Wilcox
15fab63e1e fs: prevent page refcount overflow in pipe_buf_get
Change pipe_buf_get() to return a bool indicating whether it succeeded
in raising the refcount of the page (if the thing in the pipe is a page).
This removes another mechanism for overflowing the page refcount.  All
callers converted to handle a failure.

Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-04-14 10:00:04 -07:00
Linus Torvalds
5f739e4a49 Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull misc vfs updates from Al Viro:
 "Assorted fixes (really no common topic here)"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: Make __vfs_write() static
  vfs: fix preadv64v2 and pwritev64v2 compat syscalls with offset == -1
  pipe: stop using ->can_merge
  splice: don't merge into linked buffers
  fs: move generic stat response attr handling to vfs_getattr_nosec
  orangefs: don't reinitialize result_mask in ->getattr
  fs/devpts: always delete dcache dentry-s in dput()
2019-03-12 13:27:20 -07:00
Shakeel Butt
60cd4bcd62 memcg: localize memcg_kmem_enabled() check
Move the memcg_kmem_enabled() checks into memcg kmem charge/uncharge
functions, so, the users don't have to explicitly check that condition.

This is purely code cleanup patch without any functional change.  Only
the order of checks in memcg_charge_slab() can potentially be changed
but the functionally it will be same.  This should not matter as
memcg_charge_slab() is not in the hot path.

Link: http://lkml.kernel.org/r/20190103161203.162375-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-03-05 21:07:15 -08:00
Jann Horn
01e7187b41 pipe: stop using ->can_merge
Al Viro pointed out that since there is only one pipe buffer type to which
new data can be appended, it isn't necessary to have a ->can_merge field in
struct pipe_buf_operations, we can just check for a magic type.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-02-01 02:01:45 -05:00
Jann Horn
a0ce2f0aa6 splice: don't merge into linked buffers
Before this patch, it was possible for two pipes to affect each other after
data had been transferred between them with tee():

============
$ cat tee_test.c

int main(void) {
  int pipe_a[2];
  if (pipe(pipe_a)) err(1, "pipe");
  int pipe_b[2];
  if (pipe(pipe_b)) err(1, "pipe");
  if (write(pipe_a[1], "abcd", 4) != 4) err(1, "write");
  if (tee(pipe_a[0], pipe_b[1], 2, 0) != 2) err(1, "tee");
  if (write(pipe_b[1], "xx", 2) != 2) err(1, "write");

  char buf[5];
  if (read(pipe_a[0], buf, 4) != 4) err(1, "read");
  buf[4] = 0;
  printf("got back: '%s'\n", buf);
}
$ gcc -o tee_test tee_test.c
$ ./tee_test
got back: 'abxx'
$
============

As suggested by Al Viro, fix it by creating a separate type for
non-mergeable pipe buffers, then changing the types of buffers in
splice_pipe_to_pipe() and link_pipe().

Cc: <stable@vger.kernel.org>
Fixes: 7c77f0b3f9 ("splice: implement pipe to pipe splicing")
Fixes: 70524490ee ("[PATCH] splice: add support for sys_tee()")
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-02-01 02:01:45 -05:00
Linus Torvalds
a66b4cd1e7 Merge branch 'work.open3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs open-related updates from Al Viro:

 - "do we need fput() or put_filp()" rules are gone - it's always fput()
   now. We keep track of that state where it belongs - in ->f_mode.

 - int *opened mess killed - in finish_open(), in ->atomic_open()
   instances and in fs/namei.c code around do_last()/lookup_open()/atomic_open().

 - alloc_file() wrappers with saner calling conventions are introduced
   (alloc_file_clone() and alloc_file_pseudo()); callers converted, with
   much simplification.

 - while we are at it, saner calling conventions for path_init() and
   link_path_walk(), simplifying things inside fs/namei.c (both on
   open-related paths and elsewhere).

* 'work.open3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits)
  few more cleanups of link_path_walk() callers
  allow link_path_walk() to take ERR_PTR()
  make path_init() unconditionally paired with terminate_walk()
  document alloc_file() changes
  make alloc_file() static
  do_shmat(): grab shp->shm_file earlier, switch to alloc_file_clone()
  new helper: alloc_file_clone()
  create_pipe_files(): switch the first allocation to alloc_file_pseudo()
  anon_inode_getfile(): switch to alloc_file_pseudo()
  hugetlb_file_setup(): switch to alloc_file_pseudo()
  ocxlflash_getfile(): switch to alloc_file_pseudo()
  cxl_getfile(): switch to alloc_file_pseudo()
  ... and switch shmem_file_setup() to alloc_file_pseudo()
  __shmem_file_setup(): reorder allocations
  new wrapper: alloc_file_pseudo()
  kill FILE_{CREATED,OPENED}
  switch atomic_open() and lookup_open() to returning 0 in all success cases
  document ->atomic_open() changes
  ->atomic_open(): return 0 in all success cases
  get rid of 'opened' in path_openat() and the helpers downstream
  ...
2018-08-13 19:58:36 -07:00
Al Viro
183266f26f new helper: alloc_file_clone()
alloc_file_clone(old_file, mode, ops): create a new struct file with
->f_path equal to that of old_file.  pipe converted.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12 10:04:28 -04:00
Al Viro
152b6372c9 create_pipe_files(): switch the first allocation to alloc_file_pseudo()
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12 10:04:27 -04:00
Al Viro
c9c554f214 alloc_file(): switch to passing O_... flags instead of FMODE_... mode
... so that it could set both ->f_flags and ->f_mode, without callers
having to set ->f_flags manually.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-12 10:02:57 -04:00
Al Viro
b10a4a9f76 create_pipe_files(): use fput() if allocation of the second file fails
... just use put_pipe_info() to get the pipe->files down to 1 and let
fput()-called pipe_release() do freeing.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-10 23:29:03 -04:00
Linus Torvalds
a11e1d432b Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL
The poll() changes were not well thought out, and completely
unexplained.  They also caused a huge performance regression, because
"->poll()" was no longer a trivial file operation that just called down
to the underlying file operations, but instead did at least two indirect
calls.

Indirect calls are sadly slow now with the Spectre mitigation, but the
performance problem could at least be largely mitigated by changing the
"->get_poll_head()" operation to just have a per-file-descriptor pointer
to the poll head instead.  That gets rid of one of the new indirections.

But that doesn't fix the new complexity that is completely unwarranted
for the regular case.  The (undocumented) reason for the poll() changes
was some alleged AIO poll race fixing, but we don't make the common case
slower and more complex for some uncommon special case, so this all
really needs way more explanations and most likely a fundamental
redesign.

[ This revert is a revert of about 30 different commits, not reverted
  individually because that would just be unnecessarily messy  - Linus ]

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-06-28 10:40:47 -07:00
Christoph Hellwig
dd67081b36 pipe: convert to ->poll_mask
Signed-off-by: Christoph Hellwig <hch@lst.de>
2018-05-26 09:16:44 +02:00
Dominik Brodowski
0a216dd1cf fs: add do_pipe2() helper; remove internal call to sys_pipe2()
Using this helper removes an in-kernel call to the sys_pipe2() syscall.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
2018-04-02 20:15:35 +02:00
Linus Torvalds
a9a08845e9 vfs: do bulk POLL* -> EPOLL* replacement
This is the mindless scripted replacement of kernel use of POLL*
variables as described by Al, done by this script:

    for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
        L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
        for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done
    done

with de-mangling cleanups yet to come.

NOTE! On almost all architectures, the EPOLL* constants have the same
values as the POLL* constants do.  But they keyword here is "almost".
For various bad reasons they aren't the same, and epoll() doesn't
actually work quite correctly in some cases due to this on Sparc et al.

The next patch from Al will sort out the final differences, and we
should be all done.

Scripted-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-11 14:34:03 -08:00
Eric Biggers
f734076181 pipe: read buffer limits atomically
The pipe buffer limits are accessed without any locking, and may be
changed at any time by the sysctl handlers.  In theory this could cause
problems for expressions like the following:

    pipe_user_pages_hard && user_bufs > pipe_user_pages_hard

...  since the assembly code might reference the 'pipe_user_pages_hard'
memory location multiple times, and if the admin removes the limit by
setting it to 0, there is a very brief window where processes could
incorrectly observe the limit to be exceeded.

Fix this by loading the limits with READ_ONCE() prior to use.

Link: http://lkml.kernel.org/r/20180111052902.14409-8-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-06 18:32:48 -08:00
Eric Biggers
c4fed5a91f pipe: simplify round_pipe_size()
round_pipe_size() calculates the number of pages the requested size
corresponds to, then rounds the page count up to the next power of 2.

However, it also rounds everything < PAGE_SIZE up to PAGE_SIZE.
Therefore, there's no need to actually translate the size into a page
count; we just need to round the size up to the next power of 2.

We do need to verify the size isn't greater than (1 << 31), since on
32-bit systems roundup_pow_of_two() would be undefined in that case.  But
that can just be combined with the UINT_MAX check which we need anyway
now.

Finally, update pipe_set_size() to not redundantly check the return value
of round_pipe_size() for the "invalid size" case twice.

Link: http://lkml.kernel.org/r/20180111052902.14409-7-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-06 18:32:48 -08:00
Eric Biggers
96e99be40e pipe: reject F_SETPIPE_SZ with size over UINT_MAX
A pipe's size is represented as an 'unsigned int'.  As expected, writing a
value greater than UINT_MAX to /proc/sys/fs/pipe-max-size fails with
EINVAL.  However, the F_SETPIPE_SZ fcntl silently truncates such values to
32 bits, rather than failing with EINVAL as expected.  (It *does* fail
with EINVAL for values above (1 << 31) but <= UINT_MAX.)

Fix this by moving the check against UINT_MAX into round_pipe_size() which
is called in both cases.

Link: http://lkml.kernel.org/r/20180111052902.14409-6-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-06 18:32:47 -08:00
Eric Biggers
9903a91c76 pipe: fix off-by-one error when checking buffer limits
With pipe-user-pages-hard set to 'N', users were actually only allowed up
to 'N - 1' buffers; and likewise for pipe-user-pages-soft.

Fix this to allow up to 'N' buffers, as would be expected.

Link: http://lkml.kernel.org/r/20180111052902.14409-5-ebiggers3@gmail.com
Fixes: b0b91d18e2 ("pipe: fix limit checking in pipe_set_size()")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Willy Tarreau <w@1wt.eu>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-06 18:32:47 -08:00
Eric Biggers
85c2dd5473 pipe: actually allow root to exceed the pipe buffer limits
pipe-user-pages-hard and pipe-user-pages-soft are only supposed to apply
to unprivileged users, as documented in both Documentation/sysctl/fs.txt
and the pipe(7) man page.

However, the capabilities are actually only checked when increasing a
pipe's size using F_SETPIPE_SZ, not when creating a new pipe.  Therefore,
if pipe-user-pages-hard has been set, the root user can run into it and be
unable to create pipes.  Similarly, if pipe-user-pages-soft has been set,
the root user can run into it and have their pipes limited to 1 page each.

Fix this by allowing the privileged override in both cases.

Link: http://lkml.kernel.org/r/20180111052902.14409-4-ebiggers3@gmail.com
Fixes: 759c01142a ("pipe: limit the per-user amount of pages allocated in pipes")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-06 18:32:47 -08:00
Eric Biggers
319e0a21bb pipe, sysctl: remove pipe_proc_fn()
pipe_proc_fn() is no longer needed, as it only calls through to
proc_dopipe_max_size().  Just put proc_dopipe_max_size() in the ctl_table
entry directly, and remove the unneeded EXPORT_SYMBOL() and the ENOSYS
stub for it.

(The reason the ENOSYS stub isn't needed is that the pipe-max-size
ctl_table entry is located directly in 'kern_table' rather than being
registered separately.  Therefore, the entry is already only defined when
the kernel is built with sysctl support.)

Link: http://lkml.kernel.org/r/20180111052902.14409-3-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-06 18:32:47 -08:00
Eric Biggers
4c2e4befb3 pipe, sysctl: drop 'min' parameter from pipe-max-size converter
Patch series "pipe: buffer limits fixes and cleanups", v2.

This series simplifies the sysctl handler for pipe-max-size and fixes
another set of bugs related to the pipe buffer limits:

- The root user wasn't allowed to exceed the limits when creating new
  pipes.

- There was an off-by-one error when checking the limits, so a limit of
  N was actually treated as N - 1.

- F_SETPIPE_SZ accepted values over UINT_MAX.

- Reading the pipe buffer limits could be racy.

This patch (of 7):

Before validating the given value against pipe_min_size,
do_proc_dopipe_max_size_conv() calls round_pipe_size(), which rounds the
value up to pipe_min_size.  Therefore, the second check against
pipe_min_size is redundant.  Remove it.

Link: http://lkml.kernel.org/r/20180111052902.14409-2-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-06 18:32:47 -08:00
Al Viro
076ccb76e1 fs: annotate ->poll() instances
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-11-27 16:20:05 -05:00
Joe Lawrence
7a8d181949 pipe: add proc_dopipe_max_size() to safely assign pipe_max_size
pipe_max_size is assigned directly via procfs sysctl:

  static struct ctl_table fs_table[] = {
          ...
          {
                  .procname       = "pipe-max-size",
                  .data           = &pipe_max_size,
                  .maxlen         = sizeof(int),
                  .mode           = 0644,
                  .proc_handler   = &pipe_proc_fn,
                  .extra1         = &pipe_min_size,
          },
          ...

  int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
                   size_t *lenp, loff_t *ppos)
  {
          ...
          ret = proc_dointvec_minmax(table, write, buf, lenp, ppos)
          ...

and then later rounded in-place a few statements later:

          ...
          pipe_max_size = round_pipe_size(pipe_max_size);
          ...

This leaves a window of time between initial assignment and rounding
that may be visible to other threads.  (For example, one thread sets a
non-rounded value to pipe_max_size while another reads its value.)

Similar reads of pipe_max_size are potentially racy:

  pipe.c :: alloc_pipe_info()
  pipe.c :: pipe_set_size()

Add a new proc_dopipe_max_size() that consolidates reading the new value
from the user buffer, verifying bounds, and calling round_pipe_size()
with a single assignment to pipe_max_size.

Link: http://lkml.kernel.org/r/1507658689-11669-4-git-send-email-joe.lawrence@redhat.com
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-17 16:10:03 -08:00
Joe Lawrence
d3f14c4858 pipe: avoid round_pipe_size() nr_pages overflow on 32-bit
round_pipe_size() contains a right-bit-shift expression which may
overflow, which would cause undefined results in a subsequent
roundup_pow_of_two() call.

  static inline unsigned int round_pipe_size(unsigned int size)
  {
          unsigned long nr_pages;

          nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
          return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
  }

PAGE_SIZE is defined as (1UL << PAGE_SHIFT), so:
  - 4 bytes wide on 32-bit (0 to 0xffffffff)
  - 8 bytes wide on 64-bit (0 to 0xffffffffffffffff)

That means that 32-bit round_pipe_size(), nr_pages may overflow to 0:

  size=0x00000000    nr_pages=0x0
  size=0x00000001    nr_pages=0x1
  size=0xfffff000    nr_pages=0xfffff
  size=0xfffff001    nr_pages=0x0         << !
  size=0xffffffff    nr_pages=0x0         << !

This is bad because roundup_pow_of_two(n) is undefined when n == 0!

64-bit is not a problem as the unsigned int size is 4 bytes wide
(similar to 32-bit) and the larger, 8 byte wide unsigned long, is
sufficient to handle the largest value of the bit shift expression:

  size=0xffffffff    nr_pages=100000

Modify round_pipe_size() to return 0 if n == 0 and updates its callers to
handle accordingly.

Link: http://lkml.kernel.org/r/1507658689-11669-3-git-send-email-joe.lawrence@redhat.com
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-17 16:10:02 -08:00
Joe Lawrence
98159d977f pipe: match pipe_max_size data type with procfs
Patch series "A few round_pipe_size() and pipe-max-size fixups", v3.

While backporting Michael's "pipe: fix limit handling" patchset to a
distro-kernel, Mikulas noticed that current upstream pipe limit handling
contains a few problems:

  1 - procfs signed wrap: echo'ing a large number into
      /proc/sys/fs/pipe-max-size and then cat'ing it back out shows a
      negative value.

  2 - round_pipe_size() nr_pages overflow on 32bit:  this would
      subsequently try roundup_pow_of_two(0), which is undefined.

  3 - visible non-rounded pipe-max-size value: there is no mutual
      exclusion or protection between the time pipe_max_size is assigned
      a raw value from proc_dointvec_minmax() and when it is rounded.

  4 - unsigned long -> unsigned int conversion makes for potential odd
      return errors from do_proc_douintvec_minmax_conv() and
      do_proc_dopipe_max_size_conv().

This version underwent the same testing as v1:
https://marc.info/?l=linux-kernel&m=150643571406022&w=2

This patch (of 4):

pipe_max_size is defined as an unsigned int:

  unsigned int pipe_max_size = 1048576;

but its procfs/sysctl representation is an integer:

  static struct ctl_table fs_table[] = {
          ...
          {
                  .procname       = "pipe-max-size",
                  .data           = &pipe_max_size,
                  .maxlen         = sizeof(int),
                  .mode           = 0644,
                  .proc_handler   = &pipe_proc_fn,
                  .extra1         = &pipe_min_size,
          },
          ...

that is signed:

  int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
                   size_t *lenp, loff_t *ppos)
  {
          ...
          ret = proc_dointvec_minmax(table, write, buf, lenp, ppos)

This leads to signed results via procfs for large values of pipe_max_size:

  % echo 2147483647 >/proc/sys/fs/pipe-max-size
  % cat /proc/sys/fs/pipe-max-size
  -2147483648

Use unsigned operations on this variable to avoid such negative values.

Link: http://lkml.kernel.org/r/1507658689-11669-2-git-send-email-joe.lawrence@redhat.com
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-17 16:10:02 -08:00
Greg Kroah-Hartman
b24413180f License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-02 11:10:55 +01:00
David Howells
cdf01226b2 VFS: Provide empty name qstr
Provide an empty name (ie. "") qstr for general use.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-07-06 03:27:09 -04:00
Linus Torvalds
7c0f6ba682 Replace <asm/uaccess.h> with <linux/uaccess.h> globally
This was entirely automated, using the script by Al:

  PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*<asm/uaccess.h>'
  sed -i -e "s!$PATT!#include <linux/uaccess.h>!" \
        $(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h)

to do the replacement at the end of the merge window.

Requested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-24 11:46:01 -08:00
Michael Kerrisk (man-pages)
086e774a57 pipe: cap initial pipe capacity according to pipe-max-size limit
This is a patch that provides behavior that is more consistent, and
probably less surprising to users. I consider the change optional, and
welcome opinions about whether it should be applied.

By default, pipes are created with a capacity of 64 kiB.  However,
/proc/sys/fs/pipe-max-size may be set smaller than this value.  In this
scenario, an unprivileged user could thus create a pipe whose initial
capacity exceeds the limit. Therefore, it seems logical to cap the
initial pipe capacity according to the value of pipe-max-size.

The test program shown earlier in this patch series can be used to
demonstrate the effect of the change brought about with this patch:

    # cat /proc/sys/fs/pipe-max-size
    1048576
    # sudo -u mtk ./test_F_SETPIPE_SZ 1
    Initial pipe capacity: 65536
    # echo 10000 > /proc/sys/fs/pipe-max-size
    # cat /proc/sys/fs/pipe-max-size
    16384
    # sudo -u mtk ./test_F_SETPIPE_SZ 1
    Initial pipe capacity: 16384
    # ./test_F_SETPIPE_SZ 1
    Initial pipe capacity: 65536

The last two executions of 'test_F_SETPIPE_SZ' show that pipe-max-size
caps the initial allocation for a new pipe for unprivileged users, but
not for privileged users.

Link: http://lkml.kernel.org/r/31dc7064-2a17-9c5b-1df1-4e3012ee992c@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 15:06:32 -07:00
Michael Kerrisk (man-pages)
9c87bcf0a3 pipe: make account_pipe_buffers() return a value, and use it
This is an optional patch, to provide a small performance
improvement.  Alter account_pipe_buffers() so that it returns the
new value in user->pipe_bufs. This means that we can refactor
too_many_pipe_buffers_soft() and too_many_pipe_buffers_hard() to
avoid the costs of repeated use of atomic_long_read() to get the
value user->pipe_bufs.

Link: http://lkml.kernel.org/r/93e5f193-1e5e-3e1f-3a20-eae79b7e1310@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 15:06:32 -07:00
Michael Kerrisk (man-pages)
a005ca0e68 pipe: fix limit checking in alloc_pipe_info()
The limit checking in alloc_pipe_info() (used by pipe(2) and when
opening a FIFO) has the following problems:

(1) When checking capacity required for the new pipe, the checks against
    the limit in /proc/sys/fs/pipe-user-pages-{soft,hard} are made
    against existing consumption, and exclude the memory required for
    the new pipe capacity. As a consequence: (1) the memory allocation
    throttling provided by the soft limit does not kick in quite as
    early as it should, and (2) the user can overrun the hard limit.

(2) As currently implemented, accounting and checking against the limits
    is done as follows:

    (a) Test whether the user has exceeded the limit.
    (b) Make new pipe buffer allocation.
    (c) Account new allocation against the limits.

    This is racey. Multiple processes may pass point (a) simultaneously,
    and then allocate pipe buffers that are accounted for only in step
    (c).  The race means that the user's pipe buffer allocation could be
    pushed over the limit (by an arbitrary amount, depending on how
    unlucky we were in the race). [Thanks to Vegard Nossum for spotting
    this point, which I had missed.]

This patch addresses the above problems as follows:

* Alter the checks against limits to include the memory required for the
  new pipe.
* Re-order the accounting step so that it precedes the buffer allocation.
  If the accounting step determines that a limit has been reached, revert
  the accounting and cause the operation to fail.

Link: http://lkml.kernel.org/r/8ff3e9f9-23f6-510c-644f-8e70cd1c0bd9@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 15:06:32 -07:00
Michael Kerrisk (man-pages)
09b4d19900 pipe: simplify logic in alloc_pipe_info()
Replace an 'if' block that covers most of the code in this function
with a 'goto'. This makes the code a little simpler to read, and also
simplifies the next patch (fix limit checking in alloc_pipe_info())

Link: http://lkml.kernel.org/r/aef030c1-0257-98a9-4988-186efa48530c@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 15:06:32 -07:00
Michael Kerrisk (man-pages)
b0b91d18e2 pipe: fix limit checking in pipe_set_size()
The limit checking in pipe_set_size() (used by fcntl(F_SETPIPE_SZ))
has the following problems:

(1) When increasing the pipe capacity, the checks against the limits in
    /proc/sys/fs/pipe-user-pages-{soft,hard} are made against existing
    consumption, and exclude the memory required for the increased pipe
    capacity. The new increase in pipe capacity can then push the total
    memory used by the user for pipes (possibly far) over a limit. This
    can also trigger the problem described next.

(2) The limit checks are performed even when the new pipe capacity is
    less than the existing pipe capacity. This can lead to problems if a
    user sets a large pipe capacity, and then the limits are lowered,
    with the result that the user will no longer be able to decrease the
    pipe capacity.

(3) As currently implemented, accounting and checking against the
    limits is done as follows:

    (a) Test whether the user has exceeded the limit.
    (b) Make new pipe buffer allocation.
    (c) Account new allocation against the limits.

    This is racey. Multiple processes may pass point (a)
    simultaneously, and then allocate pipe buffers that are accounted
    for only in step (c).  The race means that the user's pipe buffer
    allocation could be pushed over the limit (by an arbitrary amount,
    depending on how unlucky we were in the race). [Thanks to Vegard
    Nossum for spotting this point, which I had missed.]

This patch addresses the above problems as follows:

* Perform checks against the limits only when increasing a pipe's
  capacity; an unprivileged user can always decrease a pipe's capacity.
* Alter the checks against limits to include the memory required for
  the new pipe capacity.
* Re-order the accounting step so that it precedes the buffer
  allocation. If the accounting step determines that a limit has
  been reached, revert the accounting and cause the operation to fail.

The program below can be used to demonstrate problems 1 and 2, and the
effect of the fix. The program takes one or more command-line arguments.
The first argument specifies the number of pipes that the program should
create. The remaining arguments are, alternately, pipe capacities that
should be set using fcntl(F_SETPIPE_SZ), and sleep intervals (in
seconds) between the fcntl() operations. (The sleep intervals allow the
possibility to change the limits between fcntl() operations.)

Problem 1
=========

Using the test program on an unpatched kernel, we first set some
limits:

    # echo 0 > /proc/sys/fs/pipe-user-pages-soft
    # echo 1000000000 > /proc/sys/fs/pipe-max-size
    # echo 10000 > /proc/sys/fs/pipe-user-pages-hard    # 40.96 MB

Then show that we can set a pipe with capacity (100MB) that is
over the hard limit

    # sudo -u mtk ./test_F_SETPIPE_SZ 1 100000000
    Initial pipe capacity: 65536
        Loop 1: set pipe capacity to 100000000 bytes
            F_SETPIPE_SZ returned 134217728

Now set the capacity to 100MB twice. The second call fails (which is
probably surprising to most users, since it seems like a no-op):

    # sudo -u mtk ./test_F_SETPIPE_SZ 1 100000000 0 100000000
    Initial pipe capacity: 65536
        Loop 1: set pipe capacity to 100000000 bytes
            F_SETPIPE_SZ returned 134217728
        Loop 2: set pipe capacity to 100000000 bytes
            Loop 2, pipe 0: F_SETPIPE_SZ failed: fcntl: Operation not permitted

With a patched kernel, setting a capacity over the limit fails at the
first attempt:

    # echo 0 > /proc/sys/fs/pipe-user-pages-soft
    # echo 1000000000 > /proc/sys/fs/pipe-max-size
    # echo 10000 > /proc/sys/fs/pipe-user-pages-hard
    # sudo -u mtk ./test_F_SETPIPE_SZ 1 100000000
    Initial pipe capacity: 65536
        Loop 1: set pipe capacity to 100000000 bytes
            Loop 1, pipe 0: F_SETPIPE_SZ failed: fcntl: Operation not permitted

There is a small chance that the change to fix this problem could
break user-space, since there are cases where fcntl(F_SETPIPE_SZ)
calls that previously succeeded might fail. However, the chances are
small, since (a) the pipe-user-pages-{soft,hard} limits are new (in
4.5), and the default soft/hard limits are high/unlimited.  Therefore,
it seems warranted to make these limits operate more precisely (and
behave more like what users probably expect).

Problem 2
=========

Running the test program on an unpatched kernel, we first set some limits:

    # getconf PAGESIZE
    4096
    # echo 0 > /proc/sys/fs/pipe-user-pages-soft
    # echo 1000000000 > /proc/sys/fs/pipe-max-size
    # echo 10000 > /proc/sys/fs/pipe-user-pages-hard    # 40.96 MB

Now perform two fcntl(F_SETPIPE_SZ) operations on a single pipe,
first setting a pipe capacity (10MB), sleeping for a few seconds,
during which time the hard limit is lowered, and then set pipe
capacity to a smaller amount (5MB):

    # sudo -u mtk ./test_F_SETPIPE_SZ 1 10000000 15 5000000 &
    [1] 748
    # Initial pipe capacity: 65536
        Loop 1: set pipe capacity to 10000000 bytes
            F_SETPIPE_SZ returned 16777216
            Sleeping 15 seconds

    # echo 1000 > /proc/sys/fs/pipe-user-pages-hard      # 4.096 MB
    #     Loop 2: set pipe capacity to 5000000 bytes
            Loop 2, pipe 0: F_SETPIPE_SZ failed: fcntl: Operation not permitted

In this case, the user should be able to lower the limit.

With a kernel that has the patch below, the second fcntl()
succeeds:

    # echo 0 > /proc/sys/fs/pipe-user-pages-soft
    # echo 1000000000 > /proc/sys/fs/pipe-max-size
    # echo 10000 > /proc/sys/fs/pipe-user-pages-hard
    # sudo -u mtk ./test_F_SETPIPE_SZ 1 10000000 15 5000000 &
    [1] 3215
    # Initial pipe capacity: 65536
    #     Loop 1: set pipe capacity to 10000000 bytes
            F_SETPIPE_SZ returned 16777216
            Sleeping 15 seconds

    # echo 1000 > /proc/sys/fs/pipe-user-pages-hard

    #     Loop 2: set pipe capacity to 5000000 bytes
            F_SETPIPE_SZ returned 8388608

8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---

/* test_F_SETPIPE_SZ.c

   (C) 2016, Michael Kerrisk; licensed under GNU GPL version 2 or later

   Test operation of fcntl(F_SETPIPE_SZ) for setting pipe capacity
   and interactions with limits defined by /proc/sys/fs/pipe-* files.
*/

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

int
main(int argc, char *argv[])
{
    int (*pfd)[2];
    int npipes;
    int pcap, rcap;
    int j, p, s, stime, loop;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s num-pipes "
                "[pipe-capacity sleep-time]...\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    npipes = atoi(argv[1]);

    pfd = calloc(npipes, sizeof (int [2]));
    if (pfd == NULL) {
        perror("calloc");
        exit(EXIT_FAILURE);
    }

    for (j = 0; j < npipes; j++) {
        if (pipe(pfd[j]) == -1) {
            fprintf(stderr, "Loop %d: pipe() failed: ", j);
            perror("pipe");
            exit(EXIT_FAILURE);
        }
    }

    printf("Initial pipe capacity: %d\n", fcntl(pfd[0][0], F_GETPIPE_SZ));

    for (j = 2; j < argc; j += 2 ) {
        loop = j / 2;
        pcap = atoi(argv[j]);
        printf("    Loop %d: set pipe capacity to %d bytes\n", loop, pcap);

        for (p = 0; p < npipes; p++) {
            s = fcntl(pfd[p][0], F_SETPIPE_SZ, pcap);
            if (s == -1) {
                fprintf(stderr, "        Loop %d, pipe %d: F_SETPIPE_SZ "
                        "failed: ", loop, p);
                perror("fcntl");
                exit(EXIT_FAILURE);
            }

            if (p == 0) {
                printf("        F_SETPIPE_SZ returned %d\n", s);
                rcap = s;
            } else {
                if (s != rcap) {
                    fprintf(stderr, "        Loop %d, pipe %d: F_SETPIPE_SZ "
                            "unexpected return: %d\n", loop, p, s);
                    exit(EXIT_FAILURE);
                }
            }

            stime = (j + 1 < argc) ? atoi(argv[j + 1]) : 0;
            if (stime > 0) {
                printf("        Sleeping %d seconds\n", stime);
                sleep(stime);
            }
        }
    }

    exit(EXIT_SUCCESS);
}

8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---

Patch history:

v2
   * Switch order of test in 'if' statement to avoid function call
      (to capability()) in normal path. [This is a fix to a preexisting
      wart in the code. Thanks to Willy Tarreau]
    * Perform (size > pipe_max_size) check before calling
      account_pipe_buffers().  [Thanks to Vegard Nossum]
      Quoting Vegard:

        The potential problem happens if the user passes a very large number
        which will overflow pipe->user->pipe_bufs.

        On 32-bit, sizeof(int) == sizeof(long), so if they pass arg = INT_MAX
        then round_pipe_size() returns INT_MAX. Although it's true that the
        accounting is done in terms of pages and not bytes, so you'd need on
        the order of (1 << 13) = 8192 processes hitting the limit at the same
        time in order to make it overflow, which seems a bit unlikely.

        (See https://lkml.org/lkml/2016/8/12/215 for another discussion on the
        limit checking)

Link: http://lkml.kernel.org/r/1e464945-536b-2420-798b-e77b9c7e8593@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 15:06:32 -07:00
Michael Kerrisk (man-pages)
3734a13b96 pipe: refactor argument for account_pipe_buffers()
This is a preparatory patch for following work. account_pipe_buffers()
performs accounting in the 'user_struct'. There is no need to pass a
pointer to a 'pipe_inode_info' struct (which is then dereferenced to
obtain a pointer to the 'user' field). Instead, pass a pointer directly
to the 'user_struct'. This change is needed in preparation for a
subsequent patch that the fixes the limit checking in alloc_pipe_info()
(and the resulting code is a little more logical).

Link: http://lkml.kernel.org/r/7277bf8c-a6fc-4a7d-659c-f5b145c981ab@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 15:06:31 -07:00
Michael Kerrisk (man-pages)
d37d416664 pipe: move limit checking logic into pipe_set_size()
This is a preparatory patch for following work. Move the F_SETPIPE_SZ
limit-checking logic from pipe_fcntl() into pipe_set_size().  This
simplifies the code a little, and allows for reworking required in
a later patch that fixes the limit checking in pipe_set_size()

Link: http://lkml.kernel.org/r/3701b2c5-2c52-2c3e-226d-29b9deb29b50@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 15:06:31 -07:00
Michael Kerrisk (man-pages)
f491bd7111 pipe: relocate round_pipe_size() above pipe_set_size()
Patch series "pipe: fix limit handling", v2.

When changing a pipe's capacity with fcntl(F_SETPIPE_SZ), various limits
defined by /proc/sys/fs/pipe-* files are checked to see if unprivileged
users are exceeding limits on memory consumption.

While documenting and testing the operation of these limits I noticed
that, as currently implemented, these checks have a number of problems:

(1) When increasing the pipe capacity, the checks against the limits
    in /proc/sys/fs/pipe-user-pages-{soft,hard} are made against
    existing consumption, and exclude the memory required for the
    increased pipe capacity. The new increase in pipe capacity can then
    push the total memory used by the user for pipes (possibly far) over
    a limit. This can also trigger the problem described next.

(2) The limit checks are performed even when the new pipe capacity
    is less than the existing pipe capacity. This can lead to problems
    if a user sets a large pipe capacity, and then the limits are
    lowered, with the result that the user will no longer be able to
    decrease the pipe capacity.

(3) As currently implemented, accounting and checking against the
    limits is done as follows:

    (a) Test whether the user has exceeded the limit.
    (b) Make new pipe buffer allocation.
    (c) Account new allocation against the limits.

    This is racey. Multiple processes may pass point (a) simultaneously,
    and then allocate pipe buffers that are accounted for only in step
    (c).  The race means that the user's pipe buffer allocation could be
    pushed over the limit (by an arbitrary amount, depending on how
    unlucky we were in the race). [Thanks to Vegard Nossum for spotting
    this point, which I had missed.]

This patch series addresses these three problems.

This patch (of 8):

This is a minor preparatory patch.  After subsequent patches,
round_pipe_size() will be called from pipe_set_size(), so place
round_pipe_size() above pipe_set_size().

Link: http://lkml.kernel.org/r/91a91fdb-a959-ba7f-b551-b62477cc98a1@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-11 15:06:31 -07:00
Linus Torvalds
101105b171 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull more vfs updates from Al Viro:
 ">rename2() work from Miklos + current_time() from Deepa"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: Replace current_fs_time() with current_time()
  fs: Replace CURRENT_TIME_SEC with current_time() for inode timestamps
  fs: Replace CURRENT_TIME with current_time() for inode timestamps
  fs: proc: Delete inode time initializations in proc_alloc_inode()
  vfs: Add current_time() api
  vfs: add note about i_op->rename changes to porting
  fs: rename "rename2" i_op to "rename"
  vfs: remove unused i_op->rename
  fs: make remaining filesystems use .rename2
  libfs: support RENAME_NOREPLACE in simple_rename()
  fs: support RENAME_NOREPLACE for local filesystems
  ncpfs: fix unused variable warning
2016-10-10 20:16:43 -07:00
Miklos Szeredi
fba597db42 pipe: add pipe_buf_confirm() helper
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-10-05 18:23:59 -04:00
Miklos Szeredi
a779638cf6 pipe: add pipe_buf_release() helper
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-10-05 18:23:58 -04:00
Deepa Dinamani
078cd8279e fs: Replace CURRENT_TIME with current_time() for inode timestamps
CURRENT_TIME macro is not appropriate for filesystems as it
doesn't use the right granularity for filesystem timestamps.
Use current_time() instead.

CURRENT_TIME is also not y2038 safe.

This is also in preparation for the patch that transitions
vfs timestamps to use 64 bit time and hence make them
y2038 safe. As part of the effort current_time() will be
extended to do range checks. Hence, it is necessary for all
file system timestamps to use current_time(). Also,
current_time() will be transitioned along with vfs to be
y2038 safe.

Note that whenever a single call to current_time() is used
to change timestamps in different inodes, it is because they
share the same time granularity.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Felipe Balbi <balbi@kernel.org>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-09-27 21:06:21 -04:00
Vladimir Davydov
c4159a75b6 mm: memcontrol: only mark charged pages with PageKmemcg
To distinguish non-slab pages charged to kmemcg we mark them PageKmemcg,
which sets page->_mapcount to -512.  Currently, we set/clear PageKmemcg
in __alloc_pages_nodemask()/free_pages_prepare() for any page allocated
with __GFP_ACCOUNT, including those that aren't actually charged to any
cgroup, i.e. allocated from the root cgroup context.  To avoid overhead
in case cgroups are not used, we only do that if memcg_kmem_enabled() is
true.  The latter is set iff there are kmem-enabled memory cgroups
(online or offline).  The root cgroup is not considered kmem-enabled.

As a result, if a page is allocated with __GFP_ACCOUNT for the root
cgroup when there are kmem-enabled memory cgroups and is freed after all
kmem-enabled memory cgroups were removed, e.g.

  # no memory cgroups has been created yet, create one
  mkdir /sys/fs/cgroup/memory/test
  # run something allocating pages with __GFP_ACCOUNT, e.g.
  # a program using pipe
  dmesg | tail
  # remove the memory cgroup
  rmdir /sys/fs/cgroup/memory/test

we'll get bad page state bug complaining about page->_mapcount != -1:

  BUG: Bad page state in process swapper/0  pfn:1fd945c
  page:ffffea007f651700 count:0 mapcount:-511 mapping:          (null) index:0x0
  flags: 0x1000000000000000()

To avoid that, let's mark with PageKmemcg only those pages that are
actually charged to and hence pin a non-root memory cgroup.

Fixes: 4949148ad4 ("mm: charge/uncharge kmemcg from generic page allocator paths")
Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-09 10:14:10 -07:00
Vladimir Davydov
d86133bd39 pipe: account to kmemcg
Pipes can consume a significant amount of system memory, hence they
should be accounted to kmemcg.

This patch marks pipe_inode_info and anonymous pipe buffer page
allocations as __GFP_ACCOUNT so that they would be charged to kmemcg.
Note, since a pipe buffer page can be "stolen" and get reused for other
purposes, including mapping to userspace, we clear PageKmemcg thus
resetting page->_mapcount and uncharge it in anon_pipe_buf_steal, which
is introduced by this patch.

A note regarding anon_pipe_buf_steal implementation.  We allow to steal
the page if its ref count equals 1.  It looks racy, but it is correct
for anonymous pipe buffer pages, because:

 - We lock out all other pipe users, because ->steal is called with
   pipe_lock held, so the page can't be spliced to another pipe from
   under us.

 - The page is not on LRU and it never was.

 - Thus a parallel thread can access it only by PFN. Although this is
   quite possible (e.g. see page_idle_get_page and balloon_page_isolate)
   this is not dangerous, because all such functions do is increase page
   ref count, check if the page is the one they are looking for, and
   decrease ref count if it isn't. Since our page is clean except for
   PageKmemcg mark, which doesn't conflict with other _mapcount users,
   the worst that can happen is we see page_count > 2 due to a transient
   ref, in which case we false-positively abort ->steal, which is still
   fine, because ->steal is not guaranteed to succeed.

Link: http://lkml.kernel.org/r/20160527150313.GD26059@esperanza
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-26 16:19:19 -07:00
Kirill A. Shutemov
09cbfeaf1a mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros
PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time
ago with promise that one day it will be possible to implement page
cache with bigger chunks than PAGE_SIZE.

This promise never materialized.  And unlikely will.

We have many places where PAGE_CACHE_SIZE assumed to be equal to
PAGE_SIZE.  And it's constant source of confusion on whether
PAGE_CACHE_* or PAGE_* constant should be used in a particular case,
especially on the border between fs and mm.

Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
breakage to be doable.

Let's stop pretending that pages in page cache are special.  They are
not.

The changes are pretty straight-forward:

 - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;

 - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;

 - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};

 - page_cache_get() -> get_page();

 - page_cache_release() -> put_page();

This patch contains automated changes generated with coccinelle using
script below.  For some reason, coccinelle doesn't patch header files.
I've called spatch for them manually.

The only adjustment after coccinelle is revert of changes to
PAGE_CAHCE_ALIGN definition: we are going to drop it later.

There are few places in the code where coccinelle didn't reach.  I'll
fix them manually in a separate patch.  Comments and documentation also
will be addressed with the separate patch.

virtual patch

@@
expression E;
@@
- E << (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E

@@
expression E;
@@
- E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E

@@
@@
- PAGE_CACHE_SHIFT
+ PAGE_SHIFT

@@
@@
- PAGE_CACHE_SIZE
+ PAGE_SIZE

@@
@@
- PAGE_CACHE_MASK
+ PAGE_MASK

@@
expression E;
@@
- PAGE_CACHE_ALIGN(E)
+ PAGE_ALIGN(E)

@@
expression E;
@@
- page_cache_get(E)
+ get_page(E)

@@
expression E;
@@
- page_cache_release(E)
+ put_page(E)

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-04-04 10:41:08 -07:00
Willy Tarreau
759c01142a pipe: limit the per-user amount of pages allocated in pipes
On no-so-small systems, it is possible for a single process to cause an
OOM condition by filling large pipes with data that are never read. A
typical process filling 4000 pipes with 1 MB of data will use 4 GB of
memory. On small systems it may be tricky to set the pipe max size to
prevent this from happening.

This patch makes it possible to enforce a per-user soft limit above
which new pipes will be limited to a single page, effectively limiting
them to 4 kB each, as well as a hard limit above which no new pipes may
be created for this user. This has the effect of protecting the system
against memory abuse without hurting other users, and still allowing
pipes to work correctly though with less data at once.

The limit are controlled by two new sysctls : pipe-user-pages-soft, and
pipe-user-pages-hard. Both may be disabled by setting them to zero. The
default soft limit allows the default number of FDs per process (1024)
to create pipes of the default size (64kB), thus reaching a limit of 64MB
before starting to create only smaller pipes. With 256 processes limited
to 1024 FDs each, this results in 1024*64kB + (256*1024 - 1024) * 4kB =
1084 MB of memory allocated for a user. The hard limit is disabled by
default to avoid breaking existing applications that make intensive use
of pipes (eg: for splicing).

Reported-by: socketpair@gmail.com
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Mitigates: CVE-2013-4312 (Linux 2.0+)
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-01-19 19:25:21 -05:00
Eric Biggers
6ae0806993 fs/pipe.c: return error code rather than 0 in pipe_write()
pipe_write() would return 0 if it failed to merge the beginning of the
data to write with the last, partially filled pipe buffer.  It should
return an error code instead.  Userspace programs could be confused by
write() returning 0 when called with a nonzero 'count'.

The EFAULT error case was a regression from f0d1bec9d5 ("new helper:
copy_page_from_iter()"), while the ops->confirm() error case was a much
older bug.

Test program:

	#include <assert.h>
	#include <errno.h>
	#include <unistd.h>

	int main(void)
	{
		int fd[2];
		char data[1] = {0};

		assert(0 == pipe(fd));
		assert(1 == write(fd[1], data, 1));

		/* prior to this patch, write() returned 0 here  */
		assert(-1 == write(fd[1], NULL, 1));
		assert(errno == EFAULT);
	}

Cc: stable@vger.kernel.org # at least v3.15+
Signed-off-by: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-11-11 02:18:26 -05:00
Eric Biggers
e9bb1f9b12 fs/pipe.c: preserve alloc_file() error code
If sys_pipe() was unable to allocate a 'struct file', it always failed
with ENFILE, which means "The number of simultaneously open files in the
system would exceed a system-imposed limit." However, alloc_file()
actually returns an ERR_PTR value and might fail with other error codes.
Currently, in addition to ENFILE, it can fail with ENOMEM, potentially
when there are few open files in the system.  Update sys_pipe() to
preserve this error code.

In a prior submission of a similar patch (1) some concern was raised
about introducing a new error code for sys_pipe().  However, for most
system calls, programs cannot assume that new error codes will never be
introduced.  In addition, ENOMEM was, in fact, already a possible error
code for sys_pipe(), in the case where the file descriptor table could
not be expanded due to insufficient memory.

	(1) http://comments.gmane.org/gmane.linux.kernel/1357942

Signed-off-by: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-11-11 02:18:23 -05:00
David Howells
75c3cfa855 VFS: assorted weird filesystems: d_inode() annotations
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-04-15 15:06:58 -04:00