Re: [PATCH net] net/mlx5e: Fix use-after-free in mlx5e_tx_reporter_timeout_recover

[Matt Fleming <mfleming@cloudflare.com>]

On Wed, Apr 08, 2026 at 07:44:58PM +0100, Matt Fleming wrote:
> From: Matt Fleming <mfleming@cloudflare.com>
> 
> mlx5e_tx_reporter_timeout_recover() accesses sq->netdev after
> mlx5e_safe_reopen_channels() has torn down and freed the channel (and
> its embedded SQs). Replace the three sq->netdev references with
> priv->netdev which is safe because priv outlives channel teardown.
> 
> The netdev_err() call already used priv->netdev for this reason; make
> the trylock/unlock and health_channel_eq_recover calls consistent.
> 
> This fixes the following KASAN splat:
> 
>   BUG: KASAN: use-after-free in mlx5e_tx_reporter_timeout_recover+0x1dd/0x360 [mlx5_core]
>   Read of size 8 at addr ffff889860ed0b28 by task kworker/u113:2/5277
> 
>   Call Trace:
>    mlx5e_tx_reporter_timeout_recover+0x1dd/0x360 [mlx5_core]
>    devlink_health_reporter_recover+0xa2/0x150
>    devlink_health_report+0x254/0x7c0
>    mlx5e_reporter_tx_timeout+0x297/0x380 [mlx5_core]
>    mlx5e_tx_timeout_work+0x109/0x170 [mlx5_core]
>    process_one_work+0x677/0xf20
>    worker_thread+0x51f/0xd90
>    kthread+0x3a5/0x810
>    ret_from_fork+0x208/0x400
>    ret_from_fork_asm+0x1a/0x30
> 
> Fixes: 83ac0304a2d7 ("net/mlx5e: Fix deadlocks between devlink and netdev instance locks")
> Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
> index afdeb1b3d425..8409ae73768f 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
> @@ -160,13 +160,13 @@ static int mlx5e_tx_reporter_timeout_recover(void *ctx)
>  	 * channels are being closed for other reason and this work is not
>  	 * relevant anymore.
>  	 */
> -	while (!netdev_trylock(sq->netdev)) {
> +	while (!netdev_trylock(priv->netdev)) {
>  		if (!test_bit(MLX5E_STATE_CHANNELS_ACTIVE, &priv->state))
>  			return 0;
>  		msleep(20);
>  	}
>  
> -	err = mlx5e_health_channel_eq_recover(sq->netdev, eq, sq->cq.ch_stats);
> +	err = mlx5e_health_channel_eq_recover(priv->netdev, eq, sq->cq.ch_stats);
>  	if (!err) {
>  		to_ctx->status = 0; /* this sq recovered */
>  		goto out;
> @@ -186,7 +186,7 @@ static int mlx5e_tx_reporter_timeout_recover(void *ctx)
>  		   "mlx5e_safe_reopen_channels failed recovering from a tx_timeout, err(%d).\n",
>  		   err);
>  out:
> -	netdev_unlock(sq->netdev);
> +	netdev_unlock(priv->netdev);
>  	return err;
>  }
>  
> -- 
> 2.43.0
> 

Hey there, any thoughts on this?

Thanks,
Matt