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

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Message-ID: <Z/aQZzRYWkSLV1r/@localhost.localdomain>
Date: Wed, 9 Apr 2025 17:21:11 +0200
From: Michal Kubiak <michal.kubiak@...el.com>
To: Tariq Toukan <tariqt@...dia.com>
CC: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>, "Andrew
 Lunn" <andrew+netdev@...n.ch>, Gal Pressman <gal@...dia.com>, Leon Romanovsky
	<leonro@...dia.com>, Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky
	<leon@...nel.org>, <netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Moshe Shemesh <moshe@...dia.com>, Mark Bloch
	<mbloch@...dia.com>, Vlad Dogaru <vdogaru@...dia.com>, Yevgeny Kliteynik
	<kliteyn@...dia.com>
Subject: Re: [PATCH net-next 01/12] net/mlx5: HWS, Fix matcher action
 template attach

On Tue, Apr 08, 2025 at 05:00:45PM +0300, Tariq Toukan wrote:
> From: Vlad Dogaru <vdogaru@...dia.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@...dia.com>
> Reviewed-by: Yevgeny Kliteynik <kliteyn@...dia.com>
> Reviewed-by: Mark Bloch <mbloch@...dia.com>
> Signed-off-by: Tariq Toukan <tariqt@...dia.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);
>