Re: [PATCH net-next 01/12] net/mlx5: HWS, Fix matcher action template attach

[Vlad Dogaru]

On 4/9/25 17:21, Michal Kubiak wrote:
> On Tue, Apr 08, 2025 at 05:00:45PM +0300, Tariq Toukan wrote:
> > From: Vlad Dogaru <vdogaru@xxxxxxxxxx>
> >
> > The procedure of attaching an action template to an existing matcher had
> > a few issues:
> >
> > 1. Attaching accidentally overran the `at` array in bwc_matcher, which
> >     would result in memory corruption. This bug wasn't triggered, but it
> >     is possible to trigger it by attaching action templates beyond the
> >     initial buffer size of 8. Fix this by converting to a dynamically
> >     sized buffer and reallocating if needed.
> >
> > 2. Similarly, the `at` array inside the native matcher was never
> >     reallocated. Fix this the same as above.
> >
> > 3. The bwc layer treated any error in action template attach as a signal
> >     that the matcher should be rehashed to account for a larger number of
> >     action STEs. In reality, there are other unrelated errors that can
> >     arise and they should be propagated upstack. Fix this by adding a
> >     `need_rehash` output parameter that's orthogonal to error codes.
> >
> > Fixes: 2111bb970c78 ("net/mlx5: HWS, added backward-compatible API handling")
> > Signed-off-by: Vlad Dogaru <vdogaru@xxxxxxxxxx>
> > Reviewed-by: Yevgeny Kliteynik <kliteyn@xxxxxxxxxx>
> > Reviewed-by: Mark Bloch <mbloch@xxxxxxxxxx>
> > Signed-off-by: Tariq Toukan <tariqt@xxxxxxxxxx>
>
> In general the patch looks OK to me.
> Just one request for clarification inline.

Thank you for reviewing.

> > ---
> >   .../mellanox/mlx5/core/steering/hws/bwc.c     | 55 ++++++++++++++++---
> >   .../mellanox/mlx5/core/steering/hws/bwc.h     |  9 ++-
> >   .../mellanox/mlx5/core/steering/hws/matcher.c | 48 +++++++++++++---
> >   .../mellanox/mlx5/core/steering/hws/matcher.h |  4 ++
> >   .../mellanox/mlx5/core/steering/hws/mlx5hws.h |  5 +-
> >   5 files changed, 97 insertions(+), 24 deletions(-)
>
> [...]
>
> > @@ -520,6 +529,23 @@ hws_bwc_matcher_extend_at(struct mlx5hws_bwc_matcher *bwc_matcher,
> >   			  struct mlx5hws_rule_action rule_actions[])
> >   {
> >   	enum mlx5hws_action_type action_types[MLX5HWS_BWC_MAX_ACTS];
> > +	void *p;
> > +
> > +	if (unlikely(bwc_matcher->num_of_at >= bwc_matcher->size_of_at_array)) {
> > +		if (bwc_matcher->size_of_at_array >= MLX5HWS_MATCHER_MAX_AT)
> > +			return -ENOMEM;
> > +		bwc_matcher->size_of_at_array *= 2;
>
> Is it possible that `num_of_at` is even greater than twice `size_of_array`?
> If so, shouldn't you calculate how many multiplications by 2 you need to
> do?

We only extend the array by one template at a time, immediately after 
this check, so this can't happen.

Cheers,
Vlad