netdev - Re: [PATCH net v2 1/2] vsock: Orphan socket after transport release

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Message-ID: <zboo362son7nvmvoigmcj2v23gdcdpb364sxqzo5xndxuqqnmy@27cgbg6bxte2>
Date: Mon, 10 Feb 2025 11:15:47 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Michal Luczaj <mhal@...x.co>
Cc: "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, 
	syzbot+9d55b199192a4be7d02c@...kaller.appspotmail.com, Luigi Leonardi <leonardi@...hat.com>
Subject: Re: [PATCH net v2 1/2] vsock: Orphan socket after transport release

On Thu, Feb 06, 2025 at 12:06:47AM +0100, Michal Luczaj wrote:
>During socket release, sock_orphan() is called without considering that it
>sets sk->sk_wq to NULL. Later, if SO_LINGER is enabled, this leads to a
>null pointer dereferenced in virtio_transport_wait_close().
>
>Orphan the socket only after transport release.
>
>While there, reflow the other comment.
>
>Partially reverts the 'Fixes:' commit.
>
>KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
> lock_acquire+0x19e/0x500
> _raw_spin_lock_irqsave+0x47/0x70
> add_wait_queue+0x46/0x230
> virtio_transport_release+0x4e7/0x7f0
> __vsock_release+0xfd/0x490
> vsock_release+0x90/0x120
> __sock_release+0xa3/0x250
> sock_close+0x14/0x20
> __fput+0x35e/0xa90
> __x64_sys_close+0x78/0xd0
> do_syscall_64+0x93/0x1b0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>Reported-by: syzbot+9d55b199192a4be7d02c@...kaller.appspotmail.com
>Closes: https://syzkaller.appspot.com/bug?extid=9d55b199192a4be7d02c
>Fixes: fcdd2242c023 ("vsock: Keep the binding until socket destruction")
>Tested-by: Luigi Leonardi <leonardi@...hat.com>
>Signed-off-by: Michal Luczaj <mhal@...x.co>
>---
> net/vmw_vsock/af_vsock.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 075695173648d3a4ecbd04e908130efdbb393b41..85d20891b771a25b8172a163983054a2557f98c1 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -817,20 +817,25 @@ static void __vsock_release(struct sock *sk, int level)
> 	vsk = vsock_sk(sk);
> 	pending = NULL;	/* Compiler warning. */
>
>-	/* When "level" is SINGLE_DEPTH_NESTING, use the nested
>-	 * version to avoid the warning "possible recursive locking
>-	 * detected". When "level" is 0, lock_sock_nested(sk, level)
>-	 * is the same as lock_sock(sk).
>+	/* When "level" is SINGLE_DEPTH_NESTING, use the nested version to avoid
>+	 * the warning "possible recursive locking detected". When "level" is 0,
>+	 * lock_sock_nested(sk, level) is the same as lock_sock(sk).

This comment is formatted “weird” because recently in commit
135ffc7becc8 ("bpf, vsock: Invoke proto::close on close()") we reduced
the indentation without touching the comment.

Since this is a fix we may have to backport into stable branches without
that commit, I would avoid touching it to avoid unnecessary conflicts.

The rest LGTM!

Thanks for the quick fix and sorry for the late reply but FOSDEM-flu
caught me.

Thanks,
Stefano

> 	 */
> 	lock_sock_nested(sk, level);
>
>-	sock_orphan(sk);
>+	/* Indicate to vsock_remove_sock() that the socket is being released and
>+	 * can be removed from the bound_table. Unlike transport reassignment
>+	 * case, where the socket must remain bound despite vsock_remove_sock()
>+	 * being called from the transport release() callback.
>+	 */
>+	sock_set_flag(sk, SOCK_DEAD);
>
> 	if (vsk->transport)
> 		vsk->transport->release(vsk);
> 	else if (sock_type_connectible(sk->sk_type))
> 		vsock_remove_sock(vsk);
>
>+	sock_orphan(sk);
> 	sk->sk_shutdown = SHUTDOWN_MASK;
>
> 	skb_queue_purge(&sk->sk_receive_queue);
>
>-- 
>2.48.1
>