vringh: Use wiov->used to check for read/write desc order

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@codeaurora.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Neeraj Upadhyay 2021-06-25 08:55:02 +05:30 committed by Michael S. Tsirkin
parent cb5d2c1f6c
commit e74cfa91f4
1 changed files with 1 additions and 1 deletions

View File

@ -359,7 +359,7 @@ __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;