path: root/fs/fcntl.c
diff options
authorDesmond Cheong Zhi Xi <desmondcheongzx@gmail.com>2021-07-02 17:18:31 +0800
committerJeff Layton <jlayton@kernel.org>2021-08-21 16:20:27 -0400
commit2f488f698fda820f8e6fa0407630154eceb145d6 (patch)
tree62a61f3ec6f3227127a1572c05fd56408081d52e /fs/fcntl.c
parentfcntl: fix potential deadlocks for &fown_struct.lock (diff)
fcntl: fix potential deadlock for &fasync_struct.fa_lock
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>
Diffstat (limited to 'fs/fcntl.c')
1 files changed, 3 insertions, 2 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 932ec1e9f5bf..68added37c15 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 "
- 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);