Re: [PATCH net v2] net/mlx5: macsec: free struct mlx5_fs_id after an RCU grace period

[Paolo Abeni <pabeni@redhat.com>]

On 10/27/26 22:17, Joas Antonio dos Santos wrote:
> macsec_fs_id_del() removes a struct mlx5_fs_id from its rhashtable with
> rhashtable_remove_fast() and then frees it with kfree() right away.
> 
> The TX (SCI) table is read locklessly from the transmit path:
> mlx5e_macsec_handle_tx_skb() and mlx5e_macsec_tx_build_eseg() call
> mlx5_macsec_fs_get_fs_id_from_hashtable(), which does
> rhashtable_lookup() under rcu_read_lock() and then reads
> mlx5_fs_id->id. A transmit that looked the entry up just before it was
> removed reads freed memory.
> 
> Before commit d4ece08f4b1d ("net/mlx5: Maintain fs_id xarray per MACsec
> device inside macsec steering") the SCI table held struct
> mlx5e_macsec_sa directly, and mlx5e_macsec_del_txsa() freed it with
> kfree_rcu_mightsleep(). That commit moved the table into macsec_fs.c
> with the new struct mlx5_fs_id, but frees it with a plain kfree().
> 
> Add an rcu_head to struct mlx5_fs_id and free it with kfree_rcu().
> 
> The same issue was flagged by the Sashiko AI review as a pre-existing
> problem while reviewing the HW-GRO for PSP series.
> 
> Fixes: d4ece08f4b1d ("net/mlx5: Maintain fs_id xarray per MACsec device inside macsec steering")
> Link: https://lore.kernel.org/all/20260909065542.4B80D1F00ACA@smtp.kernel.org/
> Signed-off-by: Joas Antonio dos Santos <joasantonio108@gmail.com>
> Assisted-by: Yaga Agent HackerSec Claude:claude-opus-5-5
Waiting for an explicit ack from Mellanox.

/P