atm: Fix Use-After-Free in do_vcc_ioctl

Because do_vcc_ioctl() accesses sk->sk_receive_queue
without holding a sk->sk_receive_queue.lock, it can
cause a race with vcc_recvmsg().
A use-after-free for skb occurs with the following flow.
```
do_vcc_ioctl() -> skb_peek()
vcc_recvmsg() -> skb_recv_datagram() -> skb_free_datagram()
```
Add sk->sk_receive_queue.lock to do_vcc_ioctl() to fix this issue.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Link: https://lore.kernel.org/r/20231209094210.GA403126@v4bel-B760M-AORUS-ELITE-AX
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/atm/ioctl.c b/net/atm/ioctl.c
index 838ebf0cabbfb72f370d2794212d67466f79b81e..f81f8d56f5c0c574d60b7bb552c3cc62bca40f9e 100644 (file)
--- a/net/atm/ioctl.c
+++ b/net/atm/ioctl.c
@@ -73,14 +73,17 @@ static int do_vcc_ioctl(struct socket *sock, unsigned int cmd,
        case SIOCINQ:
        {
                struct sk_buff *skb;
+               int amount;
 
                if (sock->state != SS_CONNECTED) {
                        error = -EINVAL;
                        goto done;
                }
+               spin_lock_irq(&sk->sk_receive_queue.lock);
                skb = skb_peek(&sk->sk_receive_queue);
-               error = put_user(skb ? skb->len : 0,
-                                (int __user *)argp) ? -EFAULT : 0;
+               amount = skb ? skb->len : 0;
+               spin_unlock_irq(&sk->sk_receive_queue.lock);
+               error = put_user(amount, (int __user *)argp) ? -EFAULT : 0;
                goto done;
        }
        case ATM_SETSC: