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syslog: distinguish between /proc/kmsg and syscalls

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This allows the LSM to distinguish between syslog functions originating
from /proc/kmsg access and direct syscalls.  By default, the commoncaps
will now no longer require CAP_SYS_ADMIN to read an opened /proc/kmsg
file descriptor.  For example the kernel syslog reader can now drop
privileges after opening /proc/kmsg, instead of staying privileged with
CAP_SYS_ADMIN.  MAC systems that implement security_syslog have unchanged
behavior.

Signed-off-by: Kees Cook <kees.cook@canonical.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Kees Cook
2010-02-03 15:36:43 -08:00
committed by James Morris
parent 0719aaf5ea
commit 002345925e
8 changed files with 59 additions and 22 deletions
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14
fs/proc/kmsg.c
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@@ -12,37 +12,37 @@
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/fs.h>
#include <linux/syslog.h>
#include <asm/uaccess.h>
#include <asm/io.h>
extern wait_queue_head_t log_wait;
extern int do_syslog(int type, char __user *bug, int count);
static int kmsg_open(struct inode * inode, struct file * file)
{
return do_syslog(1,NULL,0);
return do_syslog(1, NULL, 0, SYSLOG_FROM_FILE);
}
static int kmsg_release(struct inode * inode, struct file * file)
{
(void) do_syslog(0,NULL,0);
(void) do_syslog(0, NULL, 0, SYSLOG_FROM_FILE);
return 0;
}
static ssize_t kmsg_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
if ((file->f_flags & O_NONBLOCK) && !do_syslog(9, NULL, 0))
if ((file->f_flags & O_NONBLOCK) &&
!do_syslog(9, NULL, 0, SYSLOG_FROM_FILE))
return -EAGAIN;
return do_syslog(2, buf, count);
return do_syslog(2, buf, count, SYSLOG_FROM_FILE);
}
static unsigned int kmsg_poll(struct file *file, poll_table *wait)
{
poll_wait(file, &log_wait, wait);
if (do_syslog(9, NULL, 0))
if (do_syslog(9, NULL, 0, SYSLOG_FROM_FILE))
return POLLIN | POLLRDNORM;
return 0;
}