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authorVladimir Davydov <vdavydov@parallels.com>2013-03-22 15:04:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-03-22 16:41:21 -0700
commit38d78e587d4960d0db94add518d27ee74bad2301 (patch)
tree3022cdde7ae5acd60be295f3d3fd9c78814e41c4 /ipc
parentca4b3f302c90de5e516296e581c31c80125cd24b (diff)
downloadlinux-38d78e587d4960d0db94add518d27ee74bad2301.tar.gz
mqueue: sys_mq_open: do not call mnt_drop_write() if read-only
mnt_drop_write() must be called only if mnt_want_write() succeeded, otherwise the mnt_writers counter will diverge. mnt_writers counters are used to check if remounting FS as read-only is OK, so after an extra mnt_drop_write() call, it would be impossible to remount mqueue FS as read-only. Besides, on umount a warning would be printed like this one: ===================================== [ BUG: bad unlock balance detected! ] 3.9.0-rc3 #5 Not tainted ------------------------------------- a.out/12486 is trying to release lock (sb_writers) at: mnt_drop_write+0x1f/0x30 but there are no more locks to release! Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Cc: Doug Ledford <dledford@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/mqueue.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index e5c4f609f22..3953fda2e8b 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -840,7 +840,8 @@ out_putfd:
fd = error;
}
mutex_unlock(&root->d_inode->i_mutex);
- mnt_drop_write(mnt);
+ if (!ro)
+ mnt_drop_write(mnt);
out_putname:
putname(name);
return fd;