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author | Boqun Feng <boqun.feng@gmail.com> | 2020-11-05 09:23:51 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-01-06 16:48:39 +0300 |
commit | 642c2d74c365ae8f642e50e3c141a8b8b35cc7dd (patch) | |
tree | 6a36acd7ce9be08c5e9031f462c67f61dec4c12c /fs/fcntl.c | |
parent | 5b2f1ad6b12ba8cc17b33436a92ed3a1443fa251 (diff) | |
download | linux-642c2d74c365ae8f642e50e3c141a8b8b35cc7dd.tar.xz |
fcntl: Fix potential deadlock in send_sig{io, urg}()
commit 8d1ddb5e79374fb277985a6b3faa2ed8631c5b4c upstream.
Syzbot reports a potential deadlock found by the newly added recursive
read deadlock detection in lockdep:
[...] ========================================================
[...] WARNING: possible irq lock inversion dependency detected
[...] 5.9.0-rc2-syzkaller #0 Not tainted
[...] --------------------------------------------------------
[...] syz-executor.1/10214 just changed the state of lock:
[...] ffff88811f506338 (&f->f_owner.lock){.+..}-{2:2}, at: send_sigurg+0x1d/0x200
[...] 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 ***
The corresponding deadlock case is as followed:
CPU 0 CPU 1 CPU 2
read_lock(&fown->lock);
spin_lock_irqsave(&dev->event_lock, ...)
write_lock_irq(&filp->f_owner.lock); // wait for the lock
read_lock(&fown-lock); // have to wait until the writer release
// due to the fairness
<interrupted>
spin_lock_irqsave(&dev->event_lock); // wait for the lock
The lock dependency on CPU 1 happens if there exists a call sequence:
input_inject_event():
spin_lock_irqsave(&dev->event_lock,...);
input_handle_event():
input_pass_values():
input_to_handler():
handler->event(): // evdev_event()
evdev_pass_values():
spin_lock(&client->buffer_lock);
__pass_event():
kill_fasync():
kill_fasync_rcu():
read_lock(&fa->fa_lock);
send_sigio():
read_lock(&fown->lock);
To fix this, make the reader in send_sigurg() and send_sigio() use
read_lock_irqsave() and read_lock_irqrestore().
Reported-by: syzbot+22e87cdf94021b984aa6@syzkaller.appspotmail.com
Reported-by: syzbot+c5e32344981ad9f33750@syzkaller.appspotmail.com
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/fcntl.c')
-rw-r--r-- | fs/fcntl.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c index 3d40771e8e7c..3dc90e5293e6 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -779,9 +779,10 @@ void send_sigio(struct fown_struct *fown, int fd, int band) { struct task_struct *p; enum pid_type type; + unsigned long flags; struct pid *pid; - read_lock(&fown->lock); + read_lock_irqsave(&fown->lock, flags); type = fown->pid_type; pid = fown->pid; @@ -802,7 +803,7 @@ void send_sigio(struct fown_struct *fown, int fd, int band) read_unlock(&tasklist_lock); } out_unlock_fown: - read_unlock(&fown->lock); + read_unlock_irqrestore(&fown->lock, flags); } static void send_sigurg_to_task(struct task_struct *p, @@ -817,9 +818,10 @@ int send_sigurg(struct fown_struct *fown) struct task_struct *p; enum pid_type type; struct pid *pid; + unsigned long flags; int ret = 0; - read_lock(&fown->lock); + read_lock_irqsave(&fown->lock, flags); type = fown->pid_type; pid = fown->pid; @@ -842,7 +844,7 @@ int send_sigurg(struct fown_struct *fown) read_unlock(&tasklist_lock); } out_unlock_fown: - read_unlock(&fown->lock); + read_unlock_irqrestore(&fown->lock, flags); return ret; } |