This is a note to let you know that I've just added the patch titled
appletalk: Fix Use-After-Free in atalk_ioctl
to the 5.4-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:
appletalk-fix-use-after-free-in-atalk_ioctl.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7b7a8103fc3d0082655a8efe4904b6e375f5a8bd
Author: Hyunwoo Kim <v4bel@xxxxxxxxx>
Date: Tue Dec 12 23:10:56 2023 -0500
appletalk: Fix Use-After-Free in atalk_ioctl
[ Upstream commit 189ff16722ee36ced4d2a2469d4ab65a8fee4198 ]
Because atalk_ioctl() accesses sk->sk_receive_queue
without holding a sk->sk_receive_queue.lock, it can
cause a race with atalk_recvmsg().
A use-after-free for skb occurs with the following flow.
```
atalk_ioctl() -> skb_peek()
atalk_recvmsg() -> skb_recv_datagram() -> skb_free_datagram()
```
Add sk->sk_receive_queue.lock to atalk_ioctl() to fix this issue.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Hyunwoo Kim <v4bel@xxxxxxxxx>
Link: https://lore.kernel.org/r/20231213041056.GA519680@v4bel-B760M-AORUS-ELITE-AX
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c
index 4610c352849bc..70cd5f55628d3 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -1803,15 +1803,14 @@ static int atalk_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
break;
}
case TIOCINQ: {
- /*
- * These two are safe on a single CPU system as only
- * user tasks fiddle here
- */
- struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
+ struct sk_buff *skb;
long amount = 0;
+ spin_lock_irq(&sk->sk_receive_queue.lock);
+ skb = skb_peek(&sk->sk_receive_queue);
if (skb)
amount = skb->len - sizeof(struct ddpehdr);
+ spin_unlock_irq(&sk->sk_receive_queue.lock);
rc = put_user(amount, (int __user *)argp);
break;
}
