Re: [PATCH] mm/memcg: fix UAF in drain_all_stock() async work during offline

[kernel test robot]

Hi Rik,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Rik-van-Riel/mm-memcg-fix-UAF-in-drain_all_stock-async-work-during-offline/20260827-124211
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260827124211.3b94b103%40fangorn
patch subject: [PATCH] mm/memcg: fix UAF in drain_all_stock() async work during offline
config: nios2-randconfig-r121-20260828 (https://download.01.org/0day-ci/archive/20260828/202608281724.4MTLH1h2-lkp@xxxxxxxxx/config)
compiler: nios2-linux-gcc (GCC) 8.5.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260828/202608281724.4MTLH1h2-lkp@xxxxxxxxx/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@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202608281724.4MTLH1h2-lkp@xxxxxxxxx/

sparse warnings: (new ones prefixed by >>)
>> mm/memcontrol.c:2380:6: sparse: sparse: symbol 'drain_all_stock_sync' was not declared. Should it be static?
   mm/memcontrol.c:4678:52: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/memcontrol.c:4678:52: sparse:    struct task_struct [noderef] __rcu *
   mm/memcontrol.c:4678:52: sparse:    struct task_struct *

vim +/drain_all_stock_sync +2380 mm/memcontrol.c

  2379	
> 2380	void drain_all_stock_sync(struct mem_cgroup *root_memcg)
  2381	{
  2382		/*
  2383		 * Make sure the workqueue is done with this memcg
  2384		 * before freeing it.
  2385		 */
  2386		__drain_all_stock(root_memcg, true);
  2387		flush_workqueue(memcg_wq);
  2388	}
  2389	

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