Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 53/98] mqueue: sys_mq_open: do not call mnt_drop_write() if read-only | Date | Tue, 26 Mar 2013 15:42:42 -0700 |
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3.8-stable review patch. If anyone has any objections, please let me know.
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From: Vladimir Davydov <vdavydov@parallels.com>
commit 38d78e587d4960d0db94add518d27ee74bad2301 upstream.
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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- ipc/mqueue.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- 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;
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