This is a note to let you know that I've just added the patch titled
drivers: net: slip: fix NPD bug in sl_tx_timeout()
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drivers-net-slip-fix-npd-bug-in-sl_tx_timeout.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit dadb977f8a8eadc51220468cdbc7161a246c6f57
Author: Duoming Zhou <duoming@xxxxxxxxxx>
Date: Tue Apr 5 21:22:06 2022 +0800
drivers: net: slip: fix NPD bug in sl_tx_timeout()
[ Upstream commit ec4eb8a86ade4d22633e1da2a7d85a846b7d1798 ]
When a slip driver is detaching, the slip_close() will act to
cleanup necessary resources and sl->tty is set to NULL in
slip_close(). Meanwhile, the packet we transmit is blocked,
sl_tx_timeout() will be called. Although slip_close() and
sl_tx_timeout() use sl->lock to synchronize, we don`t judge
whether sl->tty equals to NULL in sl_tx_timeout() and the
null pointer dereference bug will happen.
(Thread 1) | (Thread 2)
| slip_close()
| spin_lock_bh(&sl->lock)
| ...
... | sl->tty = NULL //(1)
sl_tx_timeout() | spin_unlock_bh(&sl->lock)
spin_lock(&sl->lock); |
... | ...
tty_chars_in_buffer(sl->tty)|
if (tty->ops->..) //(2) |
... | synchronize_rcu()
We set NULL to sl->tty in position (1) and dereference sl->tty
in position (2).
This patch adds check in sl_tx_timeout(). If sl->tty equals to
NULL, sl_tx_timeout() will goto out.
Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
Reviewed-by: Jiri Slaby <jirislaby@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220405132206.55291-1-duoming@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
index f870396e05e1..ba26fa0ceba8 100644
--- a/drivers/net/slip/slip.c
+++ b/drivers/net/slip/slip.c
@@ -471,7 +471,7 @@ static void sl_tx_timeout(struct net_device *dev)
spin_lock(&sl->lock);
if (netif_queue_stopped(dev)) {
- if (!netif_running(dev))
+ if (!netif_running(dev) || !sl->tty)
goto out;
/* May be we must check transmitter timeout here ?
