From f7ddb612568361e04d53fcd984d43d1c32c1294a Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Mon, 17 Apr 2023 22:08:50 +0900 Subject: [PATCH] zsmalloc: reset compaction source zspage pointer after putback_zspage() The current implementation of the compaction loop fails to set the source zspage pointer to NULL in all cases, leading to a potential issue where __zs_compact() could use a stale zspage pointer. This pointer could even point to a previously freed zspage, causing unexpected behavior in the putback_zspage() and migrate_write_unlock() functions after returning from the compaction loop. Address the issue by ensuring that the source zspage pointer is always set to NULL when it should be. Link: https://lkml.kernel.org/r/20230417130850.1784777-1-senozhatsky@chromium.org Fixes: 5a845e9f2d66 ("zsmalloc: rework compaction algorithm") Signed-off-by: Sergey Senozhatsky Reported-by: Yu Zhao Tested-by: Yu Zhao Reviewed-by: Yosry Ahmed Signed-off-by: Andrew Morton --- mm/zsmalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index aea50e2aa350..cc81dfba05a0 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -2239,8 +2239,8 @@ static unsigned long __zs_compact(struct zs_pool *pool, if (fg == ZS_INUSE_RATIO_0) { free_zspage(pool, class, src_zspage); pages_freed += class->pages_per_zspage; - src_zspage = NULL; } + src_zspage = NULL; if (get_fullness_group(class, dst_zspage) == ZS_INUSE_RATIO_100 || spin_is_contended(&pool->lock)) {