diff options
author | Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> | 2021-07-02 17:18:31 +0800 |
---|---|---|
committer | Jeff Layton <jlayton@kernel.org> | 2021-08-21 16:20:27 -0400 |
commit | 2f488f698fda820f8e6fa0407630154eceb145d6 (patch) | |
tree | 62a61f3ec6f3227127a1572c05fd56408081d52e /fs/fcntl.c | |
parent | f671a691e299f58835d4660d642582bf0e8f6fda (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')
-rw-r--r-- | fs/fcntl.c | 5 |
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 " "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); } } |