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

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Message-ID: <7d632b35-2a37-452f-9604-848d4145eab6@huawei.com>
Date: Mon, 26 May 2025 23:02:24 +0800
From: "dongchenchen (A)" <dongchenchen2@...wei.com>
To: Paolo Abeni <pabeni@...hat.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


在 2025/5/23 21:31, Paolo Abeni 写道:
> 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
>
I am sorry for this mistake.
recycle_stat_inc() is empty when CONFIG_PAGE_POOL_STATS is not enabled.
Maybe we can fix it as:

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 08f1b000ebc1..19c1505ec40f 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -154,8 +154,8 @@ EXPORT_SYMBOL(page_pool_ethtool_stats_get);
  
  #else
  #define alloc_stat_inc(pool, __stat)
-#define recycle_stat_inc(pool, __stat)
-#define recycle_stat_add(pool, __stat, val)
+#define recycle_stat_inc(pool, __stat)         do { } while (0)
+#define recycle_stat_add(pool, __stat, val)    do { } while (0)
  #endif

Thanks a lot!

Dong Chenchen