| From foo@baz Mon 17 Aug 2020 11:30:21 AM CEST |
| From: Stefano Garzarella <sgarzare@redhat.com> |
| Date: Wed, 12 Aug 2020 14:56:02 +0200 |
| Subject: vsock: fix potential null pointer dereference in vsock_poll() |
| |
| From: Stefano Garzarella <sgarzare@redhat.com> |
| |
| [ Upstream commit 1980c05844830a44708c98c96d600833aa3fae08 ] |
| |
| 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 |
| entry_SYSCALL_64_after_hwframe+0x44/0xa9 |
| |
| 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") |
| Reported-and-tested-by: syzbot+a61bac2fcc1a7c6623fe@syzkaller.appspotmail.com |
| Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> |
| Reviewed-by: Jorgen Hansen <jhansen@vmware.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/vmw_vsock/af_vsock.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- 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 * |
| } |
| |
| /* 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( |
