From: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com
[ Upstream commit f671a691e299f58835d4660d642582bf0e8f6fda ]
Syzbot reports a potential deadlock in do_fcntl:
======================================================== WARNING: possible irq lock inversion dependency detected 5.12.0-syzkaller #0 Not tainted -------------------------------------------------------- syz-executor132/8391 just changed the state of lock: ffff888015967bf8 (&f->f_owner.lock){.+..}-{2:2}, at: f_getown_ex fs/fcntl.c:211 [inline] ffff888015967bf8 (&f->f_owner.lock){.+..}-{2:2}, at: do_fcntl+0x8b4/0x1200 fs/fcntl.c:395 but this lock was taken by another, HARDIRQ-safe lock in the past: (&dev->event_lock){-...}-{2:2}
and interrupts could create inverse lock ordering between them.
other info that might help us debug this: Chain exists of: &dev->event_lock --> &new->fa_lock --> &f->f_owner.lock
Possible interrupt unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&f->f_owner.lock); local_irq_disable(); lock(&dev->event_lock); lock(&new->fa_lock); <Interrupt> lock(&dev->event_lock);
*** DEADLOCK ***
This happens because there is a lock hierarchy of &dev->event_lock --> &new->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,...);
However, since &dev->event_lock is HARDIRQ-safe, interrupts have to be disabled while grabbing &f->f_owner.lock, otherwise we invert the lock hierarchy.
Hence, we replace calls to read_lock/read_unlock on &f->f_owner.lock, with read_lock_irq/read_unlock_irq.
Reported-and-tested-by: syzbot+e6d5398a02c516ce5e70@syzkaller.appspotmail.com 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 | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c index 5a56351f1fc3..fcf34f83bf6a 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -149,7 +149,8 @@ void f_delown(struct file *filp) pid_t f_getown(struct file *filp) { pid_t pid = 0; - read_lock(&filp->f_owner.lock); + + read_lock_irq(&filp->f_owner.lock); rcu_read_lock(); if (pid_task(filp->f_owner.pid, filp->f_owner.pid_type)) { pid = pid_vnr(filp->f_owner.pid); @@ -157,7 +158,7 @@ pid_t f_getown(struct file *filp) pid = -pid; } rcu_read_unlock(); - read_unlock(&filp->f_owner.lock); + read_unlock_irq(&filp->f_owner.lock); return pid; }
@@ -207,7 +208,7 @@ static int f_getown_ex(struct file *filp, unsigned long arg) struct f_owner_ex owner = {}; int ret = 0;
- read_lock(&filp->f_owner.lock); + read_lock_irq(&filp->f_owner.lock); rcu_read_lock(); if (pid_task(filp->f_owner.pid, filp->f_owner.pid_type)) owner.pid = pid_vnr(filp->f_owner.pid); @@ -230,7 +231,7 @@ static int f_getown_ex(struct file *filp, unsigned long arg) ret = -EINVAL; break; } - read_unlock(&filp->f_owner.lock); + read_unlock_irq(&filp->f_owner.lock);
if (!ret) { ret = copy_to_user(owner_p, &owner, sizeof(owner)); @@ -248,10 +249,10 @@ static int f_getowner_uids(struct file *filp, unsigned long arg) uid_t src[2]; int err;
- read_lock(&filp->f_owner.lock); + read_lock_irq(&filp->f_owner.lock); src[0] = from_kuid(user_ns, filp->f_owner.uid); src[1] = from_kuid(user_ns, filp->f_owner.euid); - read_unlock(&filp->f_owner.lock); + read_unlock_irq(&filp->f_owner.lock);
err = put_user(src[0], &dst[0]); err |= put_user(src[1], &dst[1]);