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

Michal Kubiak
2025-04-09T15:21:29Z

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.

Thanks,
Michal

> ---
> .../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?

> + p = krealloc(bwc_matcher->at,
> + bwc_matcher->size_of_at_array *
> + sizeof(*bwc_matcher->at),
> + __GFP_ZERO | GFP_KERNEL);
> + if (!p) {
> + bwc_matcher->size_of_at_array /= 2;
> + return -ENOMEM;
> + }
> +
> + bwc_matcher->at = p;
> + }
>
> hws_bwc_rule_actions_to_action_types(rule_actions, action_types);
>