From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20130411202553.690236908@goodmis.org> Date: Thu, 11 Apr 2013 16:25:49 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Vladimir Davydov , Doug Ledford , KOSAKI Motohiro , "Eric W. Biederman" , Al Viro , Andrew Morton Subject: [ 046/171 ] mqueue: sys_mq_open: do not call mnt_drop_write() if read-only References: <20130411202503.783159048@goodmis.org> Content-Disposition: inline; filename=0046-mqueue-sys_mq_open-do-not-call-mnt_drop_write-if-rea.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.6.11.2 stable review patch. If anyone has any objections, please let me know. ------------------ From: Vladimir Davydov [ 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 Cc: Doug Ledford Cc: KOSAKI Motohiro Cc: "Eric W. Biederman" Cc: Al Viro Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Steven Rostedt --- 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