linux-hardening - Re: [PATCH] rcu: Annotate struct kvfree_rcu_bulk_data with __counted

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Message-ID: <ZrOUVWMRQ5q-4Xpn@pc636>
Date: Wed, 7 Aug 2024 17:35:49 +0200
From: Uladzislau Rezki <urezki@...il.com>
To: Thorsten Blum <thorsten.blum@...lux.com>
Cc: paulmck@...nel.org, frederic@...nel.org, neeraj.upadhyay@...nel.org,
	joel@...lfernandes.org, josh@...htriplett.org, boqun.feng@...il.com,
	urezki@...il.com, rostedt@...dmis.org,
	mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
	qiang.zhang1211@...il.com, kees@...nel.org, gustavoars@...nel.org,
	rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] rcu: Annotate struct kvfree_rcu_bulk_data with
 __counted_by()

On Wed, Aug 07, 2024 at 11:55:00AM +0200, Thorsten Blum wrote:
> Add the __counted_by compiler attribute to the flexible array member
> records to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> CONFIG_FORTIFY_SOURCE.
> 
> Increment nr_records before adding a new pointer to the records array.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
> ---
>  kernel/rcu/tree.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index e641cc681901..76d8d75dd8b3 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3227,7 +3227,7 @@ struct kvfree_rcu_bulk_data {
>  	struct list_head list;
>  	struct rcu_gp_oldstate gp_snap;
>  	unsigned long nr_records;
> -	void *records[];
> +	void *records[] __counted_by(nr_records);
>  };
>  
>  /*
> @@ -3767,7 +3767,8 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
>  	}
>  
>  	// Finally insert and update the GP for this page.
> -	bnode->records[bnode->nr_records++] = ptr;
> +	bnode->nr_records++;
> +	bnode->records[bnode->nr_records - 1] = ptr;
>  	get_state_synchronize_rcu_full(&bnode->gp_snap);
>  	atomic_inc(&(*krcp)->bulk_count[idx]);
>  
> -- 
> 2.45.2
> 
Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>

--
Uladzislau Rezki