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appletalk: Fix Use-After-Free in atalk_ioctl

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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: 1da177e4c3 ("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>
This commit is contained in:
Hyunwoo Kim 2023-12-12 23:10:56 -05:00 committed by Paolo Abeni
parent e23c0d21ce
commit 189ff16722
1 changed files with 4 additions and 5 deletions
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9
net/appletalk/ddp.c
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@ -1775,15 +1775,14 @@ 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;
}