target/linux/generic/backport-5.15/020-v6.2-16-mm-multi-gen-LRU-fix-crash-during-cgroup-migration.patch

   1 From c7dfefd4bdfba3d5171038d1cc2d4160288e6ee4 Mon Sep 17 00:00:00 2001
   2 From: Yu Zhao <yuzhao@google.com>
   3 Date: Sun, 15 Jan 2023 20:44:05 -0700
   4 Subject: [PATCH 16/29] mm: multi-gen LRU: fix crash during cgroup migration
   5
   6 lru_gen_migrate_mm() assumes lru_gen_add_mm() runs prior to itself.  This
   7 isn't true for the following scenario:
   8
   9     CPU 1                         CPU 2
  10
  11   clone()
  12     cgroup_can_fork()
  13                                 cgroup_procs_write()
  14     cgroup_post_fork()
  15                                   task_lock()
  16                                   lru_gen_migrate_mm()
  17                                   task_unlock()
  18     task_lock()
  19     lru_gen_add_mm()
  20     task_unlock()
  21
  22 And when the above happens, kernel crashes because of linked list
  23 corruption (mm_struct->lru_gen.list).
  24
  25 Link: https://lore.kernel.org/r/20230115134651.30028-1-msizanoen@qtmlabs.xyz/
  26 Link: https://lkml.kernel.org/r/20230116034405.2960276-1-yuzhao@google.com
  27 Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks")
  28 Signed-off-by: Yu Zhao <yuzhao@google.com>
  29 Reported-by: msizanoen <msizanoen@qtmlabs.xyz>
  30 Tested-by: msizanoen <msizanoen@qtmlabs.xyz>
  31 Cc: <stable@vger.kernel.org>    [6.1+]
  32 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  33 ---
  34  mm/vmscan.c | 5 ++++-
  35  1 file changed, 4 insertions(+), 1 deletion(-)
  36
  37 --- a/mm/vmscan.c
  38 +++ b/mm/vmscan.c
  39 @@ -3024,13 +3024,16 @@ void lru_gen_migrate_mm(struct mm_struct
  40         if (mem_cgroup_disabled())
  41                 return;
  42
  43 +       /* migration can happen before addition */
  44 +       if (!mm->lru_gen.memcg)
  45 +               return;
  46 +
  47         rcu_read_lock();
  48         memcg = mem_cgroup_from_task(task);
  49         rcu_read_unlock();
  50         if (memcg == mm->lru_gen.memcg)
  51                 return;
  52
  53 -       VM_WARN_ON_ONCE(!mm->lru_gen.memcg);
  54         VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
  55
  56         lru_gen_del_mm(mm);