netdev - Re: [PATCH net 1/5] vsock: Keep the binding until socket destruction

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Message-ID: <jy6sadpembyveqov4nyhwrnckp7k32hgxaviy5rw4dqink46lw@lqwfadqmdpbs>
Date: Mon, 20 Jan 2025 11:05:27 +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>, 
	George Zhang <georgezhang@...are.com>, Dmitry Torokhov <dtor@...are.com>, Andy King <acking@...are.com>, 
	netdev@...r.kernel.org
Subject: Re: [PATCH net 1/5] vsock: Keep the binding until socket destruction

On Fri, Jan 17, 2025 at 10:59:41PM +0100, Michal Luczaj wrote:
>Preserve sockets bindings; this includes both resulting from an explicit
>bind() and those implicitly bound through autobind during connect().
>
>Prevents socket unbinding during a transport reassignment, which fixes a
>use-after-free:
>
>    1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2)
>    2. transport->release() calls vsock_remove_bound() without checking if
>       sk was bound and moved to bound list (refcnt=1)
>    3. vsock_bind() assumes sk is in unbound list and before
>       __vsock_insert_bound(vsock_bound_sockets()) calls
>       __vsock_remove_bound() which does:
>           list_del_init(&vsk->bound_table); // nop
>           sock_put(&vsk->sk);               // refcnt=0
>
>BUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730
>Read of size 4 at addr ffff88816b46a74c by task a.out/2057
> dump_stack_lvl+0x68/0x90
> print_report+0x174/0x4f6
> kasan_report+0xb9/0x190
> __vsock_bind+0x62e/0x730
> vsock_bind+0x97/0xe0
> __sys_bind+0x154/0x1f0
> __x64_sys_bind+0x6e/0xb0
> do_syscall_64+0x93/0x1b0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>Allocated by task 2057:
> kasan_save_stack+0x1e/0x40
> kasan_save_track+0x10/0x30
> __kasan_slab_alloc+0x85/0x90
> kmem_cache_alloc_noprof+0x131/0x450
> sk_prot_alloc+0x5b/0x220
> sk_alloc+0x2c/0x870
> __vsock_create.constprop.0+0x2e/0xb60
> vsock_create+0xe4/0x420
> __sock_create+0x241/0x650
> __sys_socket+0xf2/0x1a0
> __x64_sys_socket+0x6e/0xb0
> do_syscall_64+0x93/0x1b0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>Freed by task 2057:
> kasan_save_stack+0x1e/0x40
> kasan_save_track+0x10/0x30
> kasan_save_free_info+0x37/0x60
> __kasan_slab_free+0x4b/0x70
> kmem_cache_free+0x1a1/0x590
> __sk_destruct+0x388/0x5a0
> __vsock_bind+0x5e1/0x730
> vsock_bind+0x97/0xe0
> __sys_bind+0x154/0x1f0
> __x64_sys_bind+0x6e/0xb0
> do_syscall_64+0x93/0x1b0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>refcount_t: addition on 0; use-after-free.
>WARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150
>RIP: 0010:refcount_warn_saturate+0xce/0x150
> __vsock_bind+0x66d/0x730
> vsock_bind+0x97/0xe0
> __sys_bind+0x154/0x1f0
> __x64_sys_bind+0x6e/0xb0
> do_syscall_64+0x93/0x1b0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>refcount_t: underflow; use-after-free.
>WARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150
>RIP: 0010:refcount_warn_saturate+0xee/0x150
> vsock_remove_bound+0x187/0x1e0
> __vsock_release+0x383/0x4a0
> vsock_release+0x90/0x120
> __sock_release+0xa3/0x250
> sock_close+0x14/0x20
> __fput+0x359/0xa80
> task_work_run+0x107/0x1d0
> do_exit+0x847/0x2560
> do_group_exit+0xb8/0x250
> __x64_sys_exit_group+0x3a/0x50
> x64_sys_call+0xfec/0x14f0
> do_syscall_64+0x93/0x1b0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
>Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>Signed-off-by: Michal Luczaj <mhal@...x.co>
>---
> net/vmw_vsock/af_vsock.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index fa9d1b49599bf219bdf9486741582cc8c547a354..cfe18bc8fdbe7ced073c6b3644d635fdbfa02610 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -337,7 +337,10 @@ EXPORT_SYMBOL_GPL(vsock_find_connected_socket);
>
> void vsock_remove_sock(struct vsock_sock *vsk)
> {
>-	vsock_remove_bound(vsk);
>+	/* Transport reassignment must not remove the binding. */
>+	if (sock_flag(sk_vsock(vsk), SOCK_DEAD))
>+		vsock_remove_bound(vsk);
>+

yeah, great fix!

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

> 	vsock_remove_connected(vsk);
> }
> EXPORT_SYMBOL_GPL(vsock_remove_sock);
>@@ -821,12 +824,13 @@ static void __vsock_release(struct sock *sk, int level)
> 	 */
> 	lock_sock_nested(sk, level);
>
>+	sock_orphan(sk);
>+
> 	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);
>
>-- 
>2.47.1
>