linux-kernel - [PATCH v2 3/7] ext4: avoid negative min_clusters in find_group

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Message-Id: <20240820132234.2759926-4-shikemeng@huaweicloud.com>
Date: Tue, 20 Aug 2024 21:22:30 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: tytso@....edu,
	adilger.kernel@...ger.ca
Cc: harshadshirwadkar@...il.com,
	darrick.wong@...cle.com,
	akpm@...l.org,
	shaggy@...tin.ibm.com,
	linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/7] ext4: avoid negative min_clusters in find_group_orlov()

min_clusters is signed integer and will be converted to unsigned
integer when compared with unsigned number stats.free_clusters.
If min_clusters is negative, it will be converted to a huge unsigned
value in which case all groups may not meet the actual desired free
clusters.
Set negative min_clusters to 0 to avoid unexpected behavior.

Fixes: ac27a0ec112a ("[PATCH] ext4: initial copy of files from ext3")
Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
---
 fs/ext4/ialloc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 9e2c08a8665f..81641be38c0e 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -514,6 +514,8 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
 	if (min_inodes < 1)
 		min_inodes = 1;
 	min_clusters = avefreec - EXT4_CLUSTERS_PER_GROUP(sb)*flex_size / 4;
+	if (min_clusters < 0)
+		min_clusters = 0;
 
 	/*
 	 * Start looking in the flex group where we last allocated an
-- 
2.30.0