From: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com
[ Upstream commit 2f488f698fda820f8e6fa0407630154eceb145d6 ]
There is an existing lock hierarchy of &dev->event_lock --> &fasync_struct.fa_lock --> &f->f_owner.lock from the following call chain:
input_inject_event(): spin_lock_irqsave(&dev->event_lock,...); input_handle_event(): input_pass_values(): input_to_handler(): evdev_events(): evdev_pass_values(): spin_lock(&client->buffer_lock); __pass_event(): kill_fasync(): kill_fasync_rcu(): read_lock(&fa->fa_lock); send_sigio(): read_lock_irqsave(&fown->lock,...);
&dev->event_lock is HARDIRQ-safe, so interrupts have to be disabled while grabbing &fasync_struct.fa_lock, otherwise we invert the lock hierarchy. However, since kill_fasync which calls kill_fasync_rcu is an exported symbol, it may not necessarily be called with interrupts disabled.
As kill_fasync_rcu may be called with interrupts disabled (for example, in the call chain above), we replace calls to read_lock/read_unlock on &fasync_struct.fa_lock in kill_fasync_rcu with read_lock_irqsave/read_unlock_irqrestore.
Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com Signed-off-by: Jeff Layton jlayton@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/fcntl.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c index cf9e81dfa615..887db4918a89 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -1004,13 +1004,14 @@ 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; } - read_lock(&fa->fa_lock); + read_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 @@ -1019,7 +1020,7 @@ 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); } - read_unlock(&fa->fa_lock); + read_unlock_irqrestore(&fa->fa_lock, flags); fa = rcu_dereference(fa->fa_next); } }