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Message-ID: <CANn89iJWQR62a2sk_87skv=92eegFSaBgu=W7-zn96Y5NQo8PA@mail.gmail.com>
Date: Sat, 9 Dec 2023 10:07:56 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Hyunwoo Kim <v4bel@...ori.io>
Cc: davem@...emloft.net, kuba@...nel.org, imv4bel@...il.com, pabeni@...hat.com,
netdev@...r.kernel.org
Subject: Re: [PATCH net v2] atm: Fix Use-After-Free in do_vcc_ioctl
On Sat, Dec 9, 2023 at 10:05 AM Hyunwoo Kim <v4bel@...ori.io> wrote:
>
> 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@...ori.io>
> ---
> v1 -> v2: Change the code style
> ---
> net/atm/ioctl.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/atm/ioctl.c b/net/atm/ioctl.c
> index 838ebf0cabbf..b7684abcf458 100644
> --- a/net/atm/ioctl.c
> +++ b/net/atm/ioctl.c
> @@ -72,15 +72,18 @@ static int do_vcc_ioctl(struct socket *sock, unsigned int cmd,
> goto done;
> case SIOCINQ:
> {
> + long amount;
> struct sk_buff *skb;
This should be "int amount;", and should be put after the " struct
sk_buff *skb;" line for proper style.
>
> 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:
> --
> 2.25.1
>
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