Messages in this thread Patch in this message | | | Date | Thu, 11 Apr 2013 16:25:49 -0400 | From | Steven Rostedt <> | Subject | [ 046/171 ] mqueue: sys_mq_open: do not call mnt_drop_write() if read-only |
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3.6.11.2 stable review patch. If anyone has any objections, please let me know.
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From: Vladimir Davydov <vdavydov@parallels.com>
[ Upstream commit 38d78e587d4960d0db94add518d27ee74bad2301 ]
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> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- ipc/mqueue.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/ipc/mqueue.c b/ipc/mqueue.c index 9a08acc..9e4cf7f 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -841,7 +841,8 @@ 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; -- 1.7.10.4
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