Re: [PATCH] net/mlx5: fix segmentation fault in flow destruction path

[Raslan Darawsheh <rasland@nvidia.com>]

Hi,

On 17/11/2025 9:15 AM, Maayan Kashani wrote:
> The mlx5_ipool_free() function was called with a NULL pool pointer
> during HW flow destruction, causing a segmentation fault. This occurred
> when flow creation failed and the cleanup path attempted to free
> resources from an uninitialized flow pool.
> 
> The crash happened in the following scenario:
> 1. During device start, a default NTA copy action flow is created
> 2. If the flow creation fails, mlx5_flow_hw_list_destroy() is called
> 3. In hw_cmpl_flow_update_or_destroy(), table->flow pool could be NULL
> 4. mlx5_ipool_free(table->flow, flow->idx) was called without checking
>     if table->flow is NULL
> 5. Inside mlx5_ipool_free(), accessing pool->cfg.per_core_cache caused
>     a segmentation fault due to NULL pointer dereference
> 
> The fix adds two layers of protection,
> 1. Add NULL check for table->flow before calling mlx5_ipool_free() in
>     hw_cmpl_flow_update_or_destroy(), consistent with the existing check
>     for table->resource on the previous line
> 2. Add NULL check for pool parameter in mlx5_ipool_free() as a defensive
>     measure to prevent similar crashes in other code paths
> 
> The fix also renames the ‘flow’ field in rte_flow_template_table
> to ‘flow_pool’ for better code readability.
> 
> Stack trace of the fault:
>    mlx5_ipool_free (pool=0x0) at mlx5_utils.c:753
>    hw_cmpl_flow_update_or_destroy at mlx5_flow_hw.c:4481
>    mlx5_flow_hw_destroy at mlx5_flow_hw.c:14219
>    mlx5_flow_hw_list_destroy at mlx5_flow_hw.c:14279
>    flow_hw_list_create at mlx5_flow_hw.c:14415
>    mlx5_flow_start_default at mlx5_flow.c:8263
>    mlx5_dev_start at mlx5_trigger.c:1420
> 
> Fixes: 27d171b88031 ("net/mlx5: abstract flow action and enable reconfigure")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Maayan Kashani <mkashani@nvidia.com>
> Acked-by: Bing Zhao <bingz@nvidia.com>

Patch applied to next-net-mlx,
Kindest regards
Raslan Darawsheh