Re: [PATCH] macsec: defer RX SA cleanup from RCU callback to workqueue

[Kuniyuki Iwashima <kuniyu@google.com>]

From: alexjlzheng@gmail.com
Date: Wed,  6 May 2026 18:01:07 +0800
> From: Jinliang Zheng <alexjlzheng@tencent.com>
> 
> crypto_free_aead() can call vunmap() internally (e.g. via
> dma_free_attrs() in hardware crypto drivers like hisi_sec2), which
> must not be called from softirq context.
> 
> free_rxsa() is an RCU callback and therefore runs in softirq context,
> causing a kernel crash when the underlying AEAD implementation
> performs DMA unmapping during tfm destruction:
> 
>   vunmap+0x4c/0x70
>   __iommu_dma_free+0xd0/0x138
>   dma_free_attrs+0xf4/0x100
>   sec_aead_exit+0x64/0xb8 [hisi_sec2]
>   crypto_destroy_tfm+0x98/0x110
>   free_rxsa+0x28/0x50 [macsec]
>   rcu_do_batch+0x184/0x460
>   rcu_core+0xf4/0x1f8
>   handle_softirqs+0x118/0x330
> 
> Fix this by splitting free_rxsa() into two parts: the RCU callback
> now only schedules a work item, and the actual resource release
> (crypto_free_aead, free_percpu, kfree) is done in a workqueue
> handler running in process context.
> 
> Add a destroy_work field to struct macsec_rx_sa and initialize it
> in init_rx_sa().
> 
> Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com>
> ---
>  drivers/net/macsec.c | 13 +++++++++++--
>  include/net/macsec.h |  2 ++
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
> index f6cad0746a02..dabd3d2598ae 100644
> --- a/drivers/net/macsec.c
> +++ b/drivers/net/macsec.c
> @@ -174,15 +174,23 @@ static void macsec_rxsc_put(struct macsec_rx_sc *sc)
>  		call_rcu(&sc->rcu_head, free_rx_sc_rcu);
>  }
>  
> -static void free_rxsa(struct rcu_head *head)
> +static void free_rxsa_work(struct work_struct *work)
>  {
> -	struct macsec_rx_sa *sa = container_of(head, struct macsec_rx_sa, rcu);
> +	struct macsec_rx_sa *sa = container_of(work, struct macsec_rx_sa,
> +					       destroy_work);
>  
>  	crypto_free_aead(sa->key.tfm);
>  	free_percpu(sa->stats);
>  	kfree(sa);
>  }
>  
> +static void free_rxsa(struct rcu_head *head)
> +{
> +	struct macsec_rx_sa *sa = container_of(head, struct macsec_rx_sa, rcu);
> +
> +	schedule_work(&sa->destroy_work);

rcu_work is what you want.