From: Neeraj Upadhyay <neeraju@codeaurora.org> stable inclusion from linux-4.19.206 commit 691add905f329ffdf5940d7e1b9e00c8bc89a8b8 -------------------------------- [ Upstream commit e74cfa91f42c50f7f649b0eca46aa049754ccdbd ] As __vringh_iov() traverses a descriptor chain, it populates each descriptor entry into either read or write vring iov and increments that iov's ->used member. So, as we iterate over a descriptor chain, at any point, (riov/wriov)->used value gives the number of descriptor enteries available, which are to be read or written by the device. As all read iovs must precede the write iovs, wiov->used should be zero when we are traversing a read descriptor. Current code checks for wiov->i, to figure out whether any previous entry in the current descriptor chain was a write descriptor. However, iov->i is only incremented, when these vring iovs are consumed, at a later point, and remain 0 in __vringh_iov(). So, correct the check for read and write descriptor order, to use wiov->used. Acked-by: Jason Wang <jasowang@redhat.com> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Link: https://lore.kernel.org/r/1624591502-4827-1-git-send-email-neeraju@codeauror... Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- drivers/vhost/vringh.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 59c61744dcc16..97aa9b87e5722 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -330,7 +330,7 @@ __vringh_iov(struct vringh *vrh, u16 i, iov = wiov; else { iov = riov; - if (unlikely(wiov && wiov->i)) { + if (unlikely(wiov && wiov->used)) { vringh_bad("Readable desc %p after writable", &descs[i]); err = -EINVAL; -- 2.25.1