mm: multi-gen LRU: fix crash during cgroup migration

lru_gen_migrate_mm() assumes lru_gen_add_mm() runs prior to itself.  This
isn't true for the following scenario:

    CPU 1                         CPU 2

  clone()
    cgroup_can_fork()
                                cgroup_procs_write()
    cgroup_post_fork()
                                  task_lock()
                                  lru_gen_migrate_mm()
                                  task_unlock()
    task_lock()
    lru_gen_add_mm()
    task_unlock()

And when the above happens, kernel crashes because of linked list
corruption (mm_struct->lru_gen.list).

Link: https://lore.kernel.org/r/[email protected]/
Link: https://lkml.kernel.org/r/[email protected]
Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks")
Signed-off-by: Yu Zhao <[email protected]>
Reported-by: msizanoen <[email protected]>
Tested-by: msizanoen <[email protected]>
Cc: <[email protected]>	[6.1+]
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions