linux-kernel - [PATCH] lib/lru_cache: Fixed array overflow caused by incorrect boundary handling.

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Message-Id: <20220723075931.163245-1-sanpeqf@gmail.com>
Date:   Sat, 23 Jul 2022 15:59:31 +0800
From:   John Sanpe <sanpeqf@...il.com>
To:     philipp.reisner@...bit.com, lars.ellenberg@...bit.com,
        christoph.boehmwalder@...bit.com
Cc:     drbd-dev@...ts.linbit.com, linux-kernel@...r.kernel.org,
        John Sanpe <sanpeqf@...il.com>
Subject: [PATCH] lib/lru_cache: Fixed array overflow caused by incorrect boundary handling.

This problem occurs when malloc element failed on the first time.
At this time, the counter i is 0. When it's released, we subtract 1
in advance without checking, which will cause i to become UINT_MAX,
resulting in array overflow.

Signed-off-by: John Sanpe <sanpeqf@...il.com>
---
 lib/lru_cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/lru_cache.c b/lib/lru_cache.c
index 52313acbfa62..04d95de92602 100644
--- a/lib/lru_cache.c
+++ b/lib/lru_cache.c
@@ -147,7 +147,7 @@ struct lru_cache *lc_create(const char *name, struct kmem_cache *cache,
 		return lc;
 
 	/* else: could not allocate all elements, give up */
-	for (i--; i; i--) {
+	while (i--) {
 		void *p = element[i];
 		kmem_cache_free(cache, p - e_off);
 	}
-- 
2.36.1