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

From: Michal Kubiak <[email-masked]>
Date: Wed, 9 Apr 2025 18:00:52 +0200

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 <[email-masked]>
> > > 
> > > 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 <[email-masked]>
> > > Reviewed-by: Yevgeny Kliteynik <[email-masked]>
> > > Reviewed-by: Mark Bloch <[email-masked]>
> > > Signed-off-by: Tariq Toukan <[email-masked]>
> > 
> > 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 <[email-masked]>