linux-kernel - [PATCH] ext4: avoid to access uninitialized block

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Message-Id: <20230320212106.4164212-1-shikemeng@huaweicloud.com>
Date:   Tue, 21 Mar 2023 05:21:06 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     error27@...il.com, jack@...e.cz, shikemeng@...weicloud.com
Subject: [PATCH] ext4: avoid to access uninitialized block_cluster

If inode bitmap block and block bitmap block are in different group,
there is a risk to access uninitialized block_cluster in
ext4_num_overhead_clusters. Initialize block_cluster to -1 to fix this.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <error27@...il.com>
Link: https://lore.kernel.org/r/202303171446.eLEhZzAu-lkp@intel.com/
Fixes: e3c70113e2cb ("ext4: improve inode table blocks counting in ext4_num_overhead_clusters")
---
 fs/ext4/balloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 49fdb758b0e4..094269488183 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -89,7 +89,7 @@ static unsigned ext4_num_overhead_clusters(struct super_block *sb,
 					   struct ext4_group_desc *gdp)
 {
 	unsigned base_clusters, num_clusters;
-	int block_cluster, inode_cluster;
+	int block_cluster = -1, inode_cluster;
 	int itbl_cluster_start = -1, itbl_cluster_end = -1;
 	ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
 	ext4_fsblk_t end = start + EXT4_BLOCKS_PER_GROUP(sb) - 1;
-- 
2.30.0