netdev - Re: [PATCH net] page_pool: Fix use-after-free in page_pool_recycle_in

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Message-ID: <af41c789-9e0d-4310-ae28-055beef73f10@redhat.com>
Date: Fri, 23 May 2025 15:31:22 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Dong Chenchen <dongchenchen2@...wei.com>, hawk@...nel.org,
 ilias.apalodimas@...aro.org, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, horms@...nel.org, almasrymina@...gle.com
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 zhangchangzhong@...wei.com,
 syzbot+204a4382fcb3311f3858@...kaller.appspotmail.com
Subject: Re: [PATCH net] page_pool: Fix use-after-free in
 page_pool_recycle_in_ring

On 5/23/25 8:45 AM, Dong Chenchen wrote:
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 7745ad924ae2..08f1b000ebc1 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -707,19 +707,16 @@ void page_pool_return_page(struct page_pool *pool, netmem_ref netmem)
>  
>  static bool page_pool_recycle_in_ring(struct page_pool *pool, netmem_ref netmem)
>  {
> +	bool in_softirq;
>  	int ret;
>  	/* BH protection not needed if current is softirq */
> -	if (in_softirq())
> -		ret = ptr_ring_produce(&pool->ring, (__force void *)netmem);
> -	else
> -		ret = ptr_ring_produce_bh(&pool->ring, (__force void *)netmem);
> -
> -	if (!ret) {
> +	in_softirq = page_pool_producer_lock(pool);
> +	ret = !__ptr_ring_produce(&pool->ring, (__force void *)netmem);
> +	if (ret)
>  		recycle_stat_inc(pool, ring);
> -		return true;
> -	}

Does not build in our CI:

net/core/page_pool.c: In function ‘page_pool_recycle_in_ring’:
net/core/page_pool.c:750:45: error: suggest braces around empty body in
an ‘if’ statement [-Werror=empty-body]
  750 |                 recycle_stat_inc(pool, ring);
      |                                             ^

/P