Commit 580ff9f5 authored Dec 12, 2023 by Hyunwoo Kim Committed by Greg Kroah-Hartman Dec 20, 2023

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: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Link: https://lore.kernel.org/r/20231213041056.GA519680@v4bel-B760M-AORUS-ELITE-AX


Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent bc786d62

net/appletalk/ddp.c

+4 −5

Original line number	Diff line number	Diff line
		@@ -1808,15 +1808,14 @@ 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;
		}