5.4-stable review patch. If anyone has any objections, please let me know.
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From: Hyunwoo Kim v4bel@theori.io
[ 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@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 --- net/appletalk/ddp.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
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; }