Re: general protection fault in tomoyo_socket_sendmsg_permission

On 2021/02/11 3:17, Shuah Khan wrote:

I am looking to understand the syzbot configuration and a reproducer
to be able to debug and fix the problem. How is syzbot triggering the
vhci_hcd attach and detach sequence?

I don't know. I'm waiting for syzbot to reproduce the problem on linux-next
with https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/usb/usbip?id=f1bdf414e7dd0cbc26460425719fc3ea479947a2 .

This helps me determine all these fix suggestions that are coming in
are fixes or papering over a real problem.

What are these fix suggestions?

"general protection fault in tomoyo_socket_sendmsg_permission" is a NULL pointer
dereference which can happen if vhci_device_reset() and/or vhci_device_init()
(which does vdev->ud.tcp_socket = NULL;) were unexpectedly called. There is no
reproducer, and (as far as I know) no fix suggestion.

"KASAN: null-ptr-deref Write in vhci_shutdown_connection" is an ERR_PTR(-EINTR)
pointer dereference which can happen if kthread_create() was SIGKILLed. There is
a reproducer, and https://lkml.kernel.org/r/20210205135707.4574-1-penguin-kernel@I-love.SAKURA.ne.jp
is a fix suggestion.