On Fri, Nov 07, 2014 at 10:11:14PM +0000, Al Viro wrote:
> I'm looking through the tree right now; so far it looks like we can just
> move those suckers to the point where we validate iovec and lose them
> from low-level iovec and csum copying completely. I still haven't finished
> tracing all possible paths for address to arrive at the points where we
> currently check that stuff, but so far it looks very doable.
Definitely doable. The only remaining interesting part is drivers/vhost
with the stuff it puts in vq->iov[]. If we can guarantee that it satisfies
the sanity checks (access_ok() and size-related ones), we are done -
making verify_iovec() use rw_copy_check_uvector() (and verify_compat_iov()
use compat_rw_copy_check_uvector()) will suffice to guarantee that none of
csum_partial_copy_fromiovecend
memcpy_fromiovec
memcpy_toiovec
memcpy_toiovecend
memcpy_fromiovecend
skb_copy_datagram_iovec
skb_copy_datagram_iter
skb_copy_datagram_from_iter
zerocopy_sg_from_iter
skb_copy_and_csum_datagram
skb_copy_and_csum_datagram_iovec
csum_and_copy_from_user
csum_and_copy_to_user
csum_partial_copy_from_user
will ever see an address that doesn't satisfy access_ok() checks. And
having looked at the data flow... we definitely want to do those checks
on intake of iovec - as it is, we usually repeat them quite a few times
for the same iovec segment, and we practically never end up _not_ doing them
for some segment of iovec, unless we hit a failure exit before we get around
to copying any data at all.
I'll finish RTFS drivers/vhost and if it turns out to be OK I'll post the
series moving those checks to the moment of copying iovec from userland,
so that kernel-side we could always rely on ->msg_iov elements having been
verified.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
