From 9b496a3ce68fcbc503500861c072d3fa2e9c6dcf Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Wed, 20 Mar 2013 15:06:48 +1100 Subject: [PATCH] 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: [ 194.714880] ===================================== [ 194.719680] [ BUG: bad unlock balance detected! ] [ 194.724488] 3.9.0-rc3 #5 Not tainted [ 194.728159] ------------------------------------- [ 194.732958] a.out/12486 is trying to release lock (sb_writers) at: [ 194.739355] [] mnt_drop_write+0x1f/0x30 [ 194.744851] 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 --- ipc/mqueue.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/ipc/mqueue.c b/ipc/mqueue.c index e5c4f609f22c..3953fda2e8bd 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; -- 2.39.5