From: Stefano Garzarella <sgarz...@redhat.com>
Date: Wed, 12 Aug 2020 14:56:02 +0200
> 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+a61bac2fcc1a7c662...@syzkaller.appspotmail.com
> Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
Applied and queued up for -stable, thank you.
