fs/fcntl.c:kill_fasync_rcu() fa_lock must be IRQ-safe

Fix a lockdep-splat-causing regression introduced by commit 989a2979205d
("fasync: RCU and fine grained locking").

kill_fasync() can be called from both process and hard-irq context, so
fa_lock must be taken with IRQs disabled.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=16230

Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Dominik Brodowski <linux@dominikbrodowski.net>
Tested-by: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Maciej Rutecki <maciej.rutecki@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: "David S. Miller" <davem@davemloft.net>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 51e11bf5708f..9d175d623aab 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -733,12 +733,14 @@ static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
 {
         while (fa) {
                 struct fown_struct *fown;
+                unsigned long flags;
+
                 if (fa->magic != FASYNC_MAGIC) {
                         printk(KERN_ERR "kill_fasync: bad magic number in "
                                "fasync_struct!\n");
                         return;
                 }
-                spin_lock(&fa->fa_lock);
+                spin_lock_irqsave(&fa->fa_lock, flags);
                 if (fa->fa_file) {
                         fown = &fa->fa_file->f_owner;
                         /* Don't send SIGURG to processes which have not set a
@@ -747,7 +749,7 @@ static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
                         if (!(sig == SIGURG && fown->signum == 0))
                                 send_sigio(fown, fa->fa_fd, band);
                 }
-                spin_unlock(&fa->fa_lock);
+                spin_unlock_irqrestore(&fa->fa_lock, flags);
                 fa = rcu_dereference(fa->fa_next);
         }
 }