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

Michal Kubiak
2025-04-09T16:01:19Z

On Wed, Apr 09, 2025 at 05:56:19PM +0200, Vlad Dogaru wrote:
> 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@nvidia.com>
> > >
> > > 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@nvidia.com>
> > > Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
> > > Reviewed-by: Mark Bloch <mbloch@nvidia.com>
> > > Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
> >
> > 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

Thank you for the clarification! Just double checking :-).

Cheers,
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>