Stefano Garzarella
2022-Feb-21 18:26 UTC
[PATCH] vhost/vsock: don't check owner in vhost_vsock_stop() while releasing
On Mon, Feb 21, 2022 at 11:33:11PM +0530, Anirudh Rayabharam wrote:>On Mon, Feb 21, 2022 at 05:44:20PM +0100, Stefano Garzarella wrote: >> On Mon, Feb 21, 2022 at 09:44:39PM +0530, Anirudh Rayabharam wrote: >> > On Mon, Feb 21, 2022 at 02:59:30PM +0100, Stefano Garzarella wrote: >> > > On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare at redhat.com> wrote: >> > > > >> > > > vhost_vsock_stop() calls vhost_dev_check_owner() to check the device >> > > > ownership. It expects current->mm to be valid. >> > > > >> > > > vhost_vsock_stop() is also called by vhost_vsock_dev_release() when >> > > > the user has not done close(), so when we are in do_exit(). In this >> > > > case current->mm is invalid and we're releasing the device, so we >> > > > should clean it anyway. >> > > > >> > > > Let's check the owner only when vhost_vsock_stop() is called >> > > > by an ioctl. >> > > > >> > > > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") >> > > > Cc: stable at vger.kernel.org >> > > > Reported-by: syzbot+1e3ea63db39f2b4440e0 at syzkaller.appspotmail.com >> > > > Signed-off-by: Stefano Garzarella <sgarzare at redhat.com> >> > > > --- >> > > > drivers/vhost/vsock.c | 14 ++++++++------ >> > > > 1 file changed, 8 insertions(+), 6 deletions(-) >> > > >> > > Reported-and-tested-by: syzbot+0abd373e2e50d704db87 at syzkaller.appspotmail.com >> > >> > I don't think this patch fixes "INFO: task hung in vhost_work_dev_flush" >> > even though syzbot says so. I am able to reproduce the issue locally >> > even with this patch applied. >> >> Are you using the sysbot reproducer or another test? >> In that case, can you share it? > >I am using the syzbot reproducer. > >> >> From the stack trace it seemed to me that the worker accesses a zone that >> has been cleaned (iotlb), so it is invalid and fails. > >Would the thread hang in that case? How?Looking at this log [1] it seems that the process is blocked on the wait_for_completion() in vhost_work_dev_flush(). Since we're not setting the backend to NULL to stop the worker, it's likely that the worker will keep running, preventing the flush work from completing. [1] https://syzkaller.appspot.com/text?tag=CrashLog&x=153f0852700000