diff options
author | Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> | 2021-07-02 17:18:30 +0800 |
---|---|---|
committer | Jeff Layton <jlayton@kernel.org> | 2021-08-21 16:20:27 -0400 |
commit | f671a691e299f58835d4660d642582bf0e8f6fda (patch) | |
tree | b0ea2fca0f8191659ccec21ee303ad4a5fdee4bd /fs/fcntl.c | |
parent | 9ff50bf2f2ff5fab01cac26d8eed21a89308e6ef (diff) |
fcntl: fix potential deadlocks for &fown_struct.lock
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>
Diffstat (limited to 'fs/fcntl.c')
-rw-r--r-- | fs/fcntl.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c index f946bec8f1f1..932ec1e9f5bf 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -150,7 +150,8 @@ 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); @@ -158,7 +159,7 @@ 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; } @@ -208,7 +209,7 @@ 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); @@ -231,7 +232,7 @@ 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)); @@ -249,10 +250,10 @@ 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]); |