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@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9d55b199192a4be7d02c
Fixes: fcdd2242c023 ("vsock: Keep the binding until socket destruction")
Tested-by: Luigi Leonardi <leonardi@redhat.com>
Reviewed-by: Luigi Leonardi <leonardi@redhat.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Link: https://patch.msgid.link/20250210-vsock-linger-nullderef-v3-1-ef6244d02b54@rbox.co
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 075695173648d3a4ecbd04e908130efdbb393b41..53a081d49d28ac1c04e7f8057c8a55e7b73cc131 100644 (file)
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -824,13 +824,19 @@ static void __vsock_release(struct sock *sk, int level)
         */
        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);