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

[kernel test robot <lkp@intel.com>]

Hi Dong,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Dong-Chenchen/page_pool-Fix-use-after-free-in-page_pool_recycle_in_ring/20250523-144323
base:   net/main
patch link:    https://lore.kernel.org/r/20250523064524.3035067-1-dongchenchen2%40huawei.com
patch subject: [PATCH net] page_pool: Fix use-after-free in page_pool_recycle_in_ring
config: x86_64-buildonly-randconfig-004-20250524 (https://download.01.org/0day-ci/archive/20250524/202505240558.ANlvx42u-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250524/202505240558.ANlvx42u-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505240558.ANlvx42u-lkp@intel.com/

All warnings (new ones prefixed by >>):

   net/core/page_pool.c: In function 'page_pool_recycle_in_ring':
>> net/core/page_pool.c:716:45: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]
     716 |                 recycle_stat_inc(pool, ring);
         |                                             ^


vim +/if +716 net/core/page_pool.c

ff7d6b27f894f1 Jesper Dangaard Brouer 2018-04-17  707  
4dec64c52e24c2 Mina Almasry           2024-06-28  708  static bool page_pool_recycle_in_ring(struct page_pool *pool, netmem_ref netmem)
ff7d6b27f894f1 Jesper Dangaard Brouer 2018-04-17  709  {
8801e4b0622139 Dong Chenchen          2025-05-23  710  	bool in_softirq;
ff7d6b27f894f1 Jesper Dangaard Brouer 2018-04-17  711  	int ret;
542bcea4be866b Qingfang DENG          2023-02-03  712  	/* BH protection not needed if current is softirq */
8801e4b0622139 Dong Chenchen          2025-05-23  713  	in_softirq = page_pool_producer_lock(pool);
8801e4b0622139 Dong Chenchen          2025-05-23  714  	ret = !__ptr_ring_produce(&pool->ring, (__force void *)netmem);
8801e4b0622139 Dong Chenchen          2025-05-23  715  	if (ret)
ad6fa1e1ab1b81 Joe Damato             2022-03-01 @716  		recycle_stat_inc(pool, ring);
8801e4b0622139 Dong Chenchen          2025-05-23  717  	page_pool_producer_unlock(pool, in_softirq);
ad6fa1e1ab1b81 Joe Damato             2022-03-01  718  
8801e4b0622139 Dong Chenchen          2025-05-23  719  	return ret;
ff7d6b27f894f1 Jesper Dangaard Brouer 2018-04-17  720  }
ff7d6b27f894f1 Jesper Dangaard Brouer 2018-04-17  721  

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