[PATCH] file: Add locking to f_getown
This has been needed for a long time, but now with the advent of a
reference counted struct pid there are real consequences for getting this
wrong.
Someone I think it was Oleg Nesterov pointed out that this construct was
missing locking, when I introduced struct pid. After taking time to review
the locking construct already present I figured out which lock needs to be
taken. The other paths that access f_owner.pid take either the f_owner
read or the write lock.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/fcntl.c b/fs/fcntl.c
index e7c66a1..e4f2616 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -305,9 +305,11 @@
pid_t f_getown(struct file *filp)
{
pid_t pid;
+ read_lock(&filp->f_owner.lock);
pid = pid_nr(filp->f_owner.pid);
if (filp->f_owner.pid_type == PIDTYPE_PGID)
pid = -pid;
+ read_unlock(&filp->f_owner.lock);
return pid;
}
