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

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Message-Id: <20250204-vsock-linger-nullderef-v1-1-6eb1760fa93e@rbox.co>
Date: Tue, 04 Feb 2025 01:29:52 +0100
From: Michal Luczaj <mhal@...x.co>
To: Stefano Garzarella <sgarzare@...hat.com>, 
 "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>
Cc: netdev@...r.kernel.org, Michal Luczaj <mhal@...x.co>, 
 syzbot+9d55b199192a4be7d02c@...kaller.appspotmail.com
Subject: [PATCH net 1/2] vsock: Orphan socket after transport release

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.

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")
Signed-off-by: Michal Luczaj <mhal@...x.co>
---
 net/vmw_vsock/af_vsock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 075695173648d3a4ecbd04e908130efdbb393b41..06250bb9afe2f253e96130b73554aae9151aaac1 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -824,13 +824,14 @@ static void __vsock_release(struct sock *sk, int level)
 	 */
 	lock_sock_nested(sk, level);

-	sock_orphan(sk);
+	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