Re: [PATCH net-next v10 05/12] virtio_net: Query and set flow filter caps

[Simon Horman <horms@kernel.org>]

On Mon, Nov 17, 2025 at 11:49:54AM -0600, Dan Jurgens wrote:
> On 11/17/25 11:16 AM, Simon Horman wrote:
> > On Wed, Nov 12, 2025 at 01:34:28PM -0600, Daniel Jurgens wrote:

...

> >> +	for (i = 0; i < ff->ff_mask->count; i++) {
> >> +		if (sel->length > MAX_SEL_LEN) {
> >> +			err = -EINVAL;
> >> +			goto err_ff_action;
> >> +		}
> >> +		real_ff_mask_size += sizeof(struct virtio_net_ff_selector) + sel->length;
> >> +		sel = (void *)sel + sizeof(*sel) + sel->length;
> >> +	}
> > 
> > Hi Daniel,
> > 
> > I'm not sure that the bounds checking in the loop above is adequate.
> > For example, if ff->ff_mask->count is larger than expected.
> > Or sel->length returns MAX_SEL_LEN each time then it seems
> > than sel could overrun the space allocated for ff->ff_mask.
> > 
> > Flagged by Claude Code with https://github.com/masoncl/review-prompts/
> > 
> 
> I can also bound the loop by VIRTIO_NET_FF_MASK_TYPE_MAX. I'll also
> address your comments about classifier and rules limits on patch 7 here,
> by checking the rules and classifier limits are > 0.

Thanks.

I think that even if the loop is bounded there is still (a much smaller)
scope for an overflow. This is because selectors isn't large enough for
VIRTIO_NET_FF_MASK_TYPE_MAX entries if all of them have length ==
MAX_SEL_LEN.

> 
> I'll wait to push a new version until I hear back from Michael about the
> threading comment he made on the cover letter.
>