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

[Vlad Dogaru <vdogaru@nvidia.com>]

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