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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
..
9p Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
adfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
affs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
afs Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-10-11 08:10:19 -07:00
autofs4 autofs: refactor ioctl fn vector in iookup_dev_ioctl() 2016-10-11 15:06:31 -07:00
befs block: remove remnant refs to hardsect 2016-09-14 08:44:57 -06:00
bfs Merge remote-tracking branch 'ovl/rename2' into for-linus 2016-10-10 23:02:51 -04:00
btrfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
cachefiles Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
ceph Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
cifs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
coda Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
configfs Merge remote-tracking branch 'ovl/rename2' into for-linus 2016-10-10 23:02:51 -04:00
cramfs
crypto Lots of bug fixes and cleanups. 2016-10-07 15:15:33 -07:00
debugfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
devpts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
dlm dlm: free workqueues after the connections 2016-10-10 09:54:00 -05:00
ecryptfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
efivarfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
efs
exofs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
exportfs
ext2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
ext4 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
f2fs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
fat Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
freevxfs
fscache
fuse Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
gfs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
hfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
hfsplus Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
hostfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
hpfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
hugetlbfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
isofs get rid of 'parent' argument of ->d_compare() 2016-07-31 16:37:25 -04:00
jbd2 jbd2: fix lockdep annotation in add_transaction_credits() 2016-09-22 11:44:06 -04:00
jffs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
jfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
kernfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
lockd Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-07-28 12:59:05 -07:00
logfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
minix Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
ncpfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
nfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
nfs_common
nfsd Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
nilfs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
nls
notify fsnotify: clean up spinlock assertions 2016-10-07 18:46:26 -07:00
ntfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
ocfs2 ocfs2: fix memory leak in dlm_migrate_request_handler() 2016-10-11 15:06:30 -07:00
omfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
openpromfs fs: Replace CURRENT_TIME with current_time() for inode timestamps 2016-09-27 21:06:21 -04:00
orangefs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
overlayfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
proc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
pstore Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
qnx4
qnx6
quota quota: fill in Q_XGETQSTAT inode information for inactive quotas 2016-08-15 17:43:31 +02:00
ramfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
reiserfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
romfs
squashfs vfs: Remove {get,set,remove}xattr inode operations 2016-10-07 21:48:36 -04:00
sysfs sysfs print name of undiscoverable attribute group 2016-09-27 12:24:29 +02:00
sysv Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
tracefs fs: Replace CURRENT_TIME with current_time() for inode timestamps 2016-09-27 21:06:21 -04:00
ubifs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
udf Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
ufs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
xfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
aio.c fs/aio.c: eliminate redundant loads in put_aio_ring_file 2016-09-27 21:45:46 -04:00
anon_inodes.c
attr.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
bad_inode.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
binfmt_aout.c
binfmt_elf_fdpic.c
binfmt_elf.c x86/coredump: Use pr_reg size, rather that TIF_IA32 flag 2016-09-14 21:28:10 +02:00
binfmt_em86.c fs/binfmt_em86.c: fix incompatible pointer type 2016-08-02 19:35:15 -04:00
binfmt_flat.c binfmt_flat: allow compressed flat binary format to work on MMU systems 2016-07-28 13:29:12 +10:00
binfmt_misc.c fs: Replace current_fs_time() with current_time() 2016-09-27 21:06:22 -04:00
binfmt_script.c
block_dev.c block: implement (some of) fallocate for block devices 2016-10-11 15:06:30 -07:00
buffer.c fs/buffer.c: make __getblk_slow() static 2016-09-27 18:47:38 -04:00
char_dev.c
compat_binfmt_elf.c
compat_ioctl.c
compat.c compat: remove compat_printk() 2016-09-27 21:20:53 -04:00
coredump.c
dax.c thp: reduce usage of huge zero page's atomic counter 2016-10-07 18:46:28 -07:00
dcache.c Merge branch 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-08-07 10:01:14 -04:00
dcookies.c
direct-io.c consistent treatment of EFAULT on O_DIRECT read/write 2016-10-03 20:38:55 -04:00
drop_caches.c
eventfd.c
eventpoll.c
exec.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/gerg/m68knommu 2016-08-04 18:04:44 -04:00
fcntl.c
fhandle.c
file_table.c
file.c fs/file: more unsigned file descriptors 2016-09-27 18:47:38 -04:00
filesystems.c
fs_pin.c
fs_struct.c
fs-writeback.c mm, writeback: flush plugged IO in wakeup_flusher_threads() 2016-08-09 19:58:06 -06:00
inode.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
internal.h Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 13:04:49 -07:00
ioctl.c vfs: cap dedupe request structure size at PAGE_SIZE 2016-09-15 13:29:52 -07:00
iomap.c Merge branch 'iomap-4.9-dax' into for-next 2016-10-03 09:53:59 +11:00
Kconfig mm/hugetlb: introduce ARCH_HAS_GIGANTIC_PAGE 2016-10-07 18:46:29 -07:00
Kconfig.binfmt ARM: 8594/1: enable binfmt_flat on systems with an MMU 2016-08-12 16:47:05 +01:00
libfs.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
locks.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
Makefile
mbcache.c mbcache: fix to detect failure of register_shrinker 2016-08-31 11:44:36 -04:00
mount.h mnt: Add a per mount namespace limit on the number of mounts 2016-09-30 12:46:48 -05:00
mpage.c block/mm: make bdev_ops->rw_page() take a bool for read/write 2016-08-07 14:41:02 -06:00
namei.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
namespace.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 13:04:49 -07:00
no-block.c
nsfs.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
open.c block: implement (some of) fallocate for block devices 2016-10-11 15:06:30 -07:00
pipe.c pipe: fix limit checking in alloc_pipe_info() 2016-10-11 15:06:32 -07:00
pnode.c mnt: Add a per mount namespace limit on the number of mounts 2016-09-30 12:46:48 -05:00
pnode.h mnt: Add a per mount namespace limit on the number of mounts 2016-09-30 12:46:48 -05:00
posix_acl.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 20:16:43 -07:00
proc_namespace.c
read_write.c
readdir.c
select.c fs/select: add vmalloc fallback for select(2) 2016-10-11 15:06:30 -07:00
seq_file.c seq/proc: modify seq_put_decimal_[u]ll to take a const char *, not char 2016-10-07 18:46:30 -07:00
signalfd.c
splice.c fix ITER_PIPE interaction with direct_IO 2016-10-10 13:36:06 -04:00
stack.c
stat.c
statfs.c
super.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2016-07-29 15:54:19 -07:00
sync.c
timerfd.c
userfaultfd.c
utimes.c Merge remote-tracking branch 'jk/vfs' into work.misc 2016-10-08 11:06:08 -04:00
xattr.c vfs: Remove {get,set,remove}xattr inode operations 2016-10-07 21:48:36 -04:00