From 14f1992430ef9e647b02aa8ca12c5bcb9a1dffea Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Thu, 25 Jan 2024 08:51:27 +0000 Subject: [PATCH] mm: zswap: fix missing folio cleanup in writeback race path commit e3b63e966cac0bf78aaa1efede1827a252815a1d upstream. In zswap_writeback_entry(), after we get a folio from __read_swap_cache_async(), we grab the tree lock again to check that the swap entry was not invalidated and recycled. If it was, we delete the folio we just added to the swap cache and exit. However, __read_swap_cache_async() returns the folio locked when it is newly allocated, which is always true for this path, and the folio is ref'd. Make sure to unlock and put the folio before returning. This was discovered by code inspection, probably because this path handles a race condition that should not happen often, and the bug would not crash the system, it will only strand the folio indefinitely. Link: https://lkml.kernel.org/r/20240125085127.1327013-1-yosryahmed@google.com Fixes: 04fc7816089c ("mm: fix zswap writeback race condition") Signed-off-by: Yosry Ahmed Reviewed-by: Chengming Zhou Acked-by: Johannes Weiner Reviewed-by: Nhat Pham Cc: Domenico Cerasuolo Cc: Signed-off-by: Andrew Morton Signed-off-by: Yosry Ahmed Signed-off-by: Greg Kroah-Hartman --- mm/zswap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/zswap.c b/mm/zswap.c index b3829ada4a41..b7cb126797f9 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1013,6 +1013,8 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) if (zswap_rb_search(&tree->rbroot, entry->offset) != entry) { spin_unlock(&tree->lock); delete_from_swap_cache(page_folio(page)); + unlock_page(page); + put_page(page); ret = -ENOMEM; goto fail; }