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| author | Miaohe Lin <linmiaohe@huawei.com> | 2021-11-05 13:45:03 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-11-26 11:36:16 +0100 |
| commit | b19675b6a046da6b4e160a78eedb3dd2584aa889 (patch) | |
| tree | de38ebc31c31d0d84d04fab5085a71619372686e /mm | |
| parent | 6abf177202ab5266b55ce298f5766f6bec8ee804 (diff) | |
| download | linux-stable-b19675b6a046da6b4e160a78eedb3dd2584aa889.tar.gz linux-stable-b19675b6a046da6b4e160a78eedb3dd2584aa889.tar.bz2 linux-stable-b19675b6a046da6b4e160a78eedb3dd2584aa889.zip | |
mm/zsmalloc.c: close race window between zs_pool_dec_isolated() and zs_unregister_migration()
[ Upstream commit afe8605ca45424629fdddfd85984b442c763dc47 ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/zsmalloc.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index d52c005a060f..11e81b3ff0cf 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1904,10 +1904,11 @@ static inline void zs_pool_dec_isolated(struct zs_pool *pool) VM_BUG_ON(atomic_long_read(&pool->isolated_pages) <= 0); atomic_long_dec(&pool->isolated_pages); /* - * There's no possibility of racing, since wait_for_isolated_drain() - * checks the isolated count under &class->lock after enqueuing - * on migration_wait. + * Checking pool->destroying must happen after atomic_long_dec() + * for pool->isolated_pages above. Paired with the smp_mb() in + * zs_unregister_migration(). */ + smp_mb__after_atomic(); if (atomic_long_read(&pool->isolated_pages) == 0 && pool->destroying) wake_up_all(&pool->migration_wait); } |