]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
mm/zsmalloc.c: close race window between zs_pool_dec_isolated() and zs_unregister_mig...
authorMiaohe Lin <linmiaohe@huawei.com>
Fri, 5 Nov 2021 20:45:03 +0000 (13:45 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 6 Nov 2021 20:30:43 +0000 (13:30 -0700)
commitafe8605ca45424629fdddfd85984b442c763dc47
treef2c1c82517c75a7d2e0f619a7027475553d81afb
parent3d88705c10677d1fc3f14786361aee649839aa7e
mm/zsmalloc.c: close race window between zs_pool_dec_isolated() and zs_unregister_migration()

There is one possible race window between zs_pool_dec_isolated() and
zs_unregister_migration() because wait_for_isolated_drain() checks the
isolated count without holding class->lock and there is no order inside
zs_pool_dec_isolated().  Thus the below race window could be possible:

  zs_pool_dec_isolated zs_unregister_migration
    check pool->destroying != 0
  pool->destroying = true;
  smp_mb();
  wait_for_isolated_drain()
    wait for pool->isolated_pages == 0
    atomic_long_dec(&pool->isolated_pages);
    atomic_long_read(&pool->isolated_pages) == 0

Since we observe the pool->destroying (false) before atomic_long_dec()
for pool->isolated_pages, waking pool->migration_wait up is missed.

Fix this by ensure checking pool->destroying happens after the
atomic_long_dec(&pool->isolated_pages).

Link: https://lkml.kernel.org/r/20210708115027.7557-1-linmiaohe@huawei.com
Fixes: 701d678599d0 ("mm/zsmalloc.c: fix race condition in zs_destroy_pool")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Henry Burns <henryburns@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/zsmalloc.c