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From: Stefano Garzarella <>
Cc:, Dexuan Cui <>,, Stefan Hajnoczi <>,
	Jakub Kicinski <>,
	Jorgen Hansen <>,
	Stefano Garzarella <>
Subject: [PATCH net v2] vsock: fix potential null pointer dereference in vsock_poll()
Date: Wed, 12 Aug 2020 14:56:02 +0200	[thread overview]
Message-ID: <> (raw)

syzbot reported this issue where in the vsock_poll() we find the
socket state at TCP_ESTABLISHED, but 'transport' is null:
  general protection fault, probably for non-canonical address 0xdffffc0000000012: 0000 [#1] PREEMPT SMP KASAN
  KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097]
  CPU: 0 PID: 8227 Comm: syz-executor.2 Not tainted 5.8.0-rc7-syzkaller #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:vsock_poll+0x75a/0x8e0 net/vmw_vsock/af_vsock.c:1038
  Call Trace:
   sock_poll+0x159/0x460 net/socket.c:1266
   vfs_poll include/linux/poll.h:90 [inline]
   do_pollfd fs/select.c:869 [inline]
   do_poll fs/select.c:917 [inline]
   do_sys_poll+0x607/0xd40 fs/select.c:1011
   __do_sys_poll fs/select.c:1069 [inline]
   __se_sys_poll fs/select.c:1057 [inline]
   __x64_sys_poll+0x18c/0x440 fs/select.c:1057
   do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384

This issue can happen if the TCP_ESTABLISHED state is set after we read
the vsk->transport in the vsock_poll().

We could put barriers to synchronize, but this can only happen during
connection setup, so we can simply check that 'transport' is valid.

Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Signed-off-by: Stefano Garzarella <>
 - removed cleanups patch from the series [David]

 net/vmw_vsock/af_vsock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 27bbcfad9c17..9e93bc201cc0 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1032,7 +1032,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
 		/* Connected sockets that can produce data can be written. */
-		if (sk->sk_state == TCP_ESTABLISHED) {
+		if (transport && sk->sk_state == TCP_ESTABLISHED) {
 			if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
 				bool space_avail_now = false;
 				int ret = transport->notify_poll_out(

             reply	other threads:[~2020-08-12 12:56 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-12 12:56 Stefano Garzarella [this message]
2020-08-12 13:33 ` [PATCH net v2] vsock: fix potential null pointer dereference in vsock_poll() Jorgen Hansen
2020-08-12 20:08 ` David Miller

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