linux-ext4 - [PATCH v2 1/9] ext4: avoid overflow when setting values via sysfs

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Date: Tue, 27 Feb 2024 17:11:40 +0800
From: Baokun Li <libaokun1@...wei.com>
To: <linux-ext4@...r.kernel.org>
CC: <tytso@....edu>, <adilger.kernel@...ger.ca>, <jack@...e.cz>,
	<ritesh.list@...il.com>, <ojaswin@...ux.ibm.com>, <adobriyan@...il.com>,
	<linux-kernel@...r.kernel.org>, <yi.zhang@...wei.com>,
	<yangerkun@...wei.com>, <libaokun1@...wei.com>
Subject: [PATCH v2 1/9] ext4: avoid overflow when setting values via sysfs

When setting values of type unsigned int through sysfs, we use kstrtoul()
to parse it and then truncate part of it as the final set value, when the
set value is greater than UINT_MAX, the set value will not match what we
see because of the truncation. As follows:

  $ echo 4294967296 > /sys/fs/ext4/sda/mb_max_linear_groups
  $ cat /sys/fs/ext4/sda/mb_max_linear_groups
    0

So we use kstrtouint() to parse the attr_pointer_ui type to avoid the
inconsistency described above. In addition, a judgment is added to avoid
setting s_resv_clusters less than 0.

Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
 fs/ext4/sysfs.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index 6d332dff79dd..ca820620b974 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -104,7 +104,7 @@ static ssize_t reserved_clusters_store(struct ext4_sb_info *sbi,
 	int ret;
 
 	ret = kstrtoull(skip_spaces(buf), 0, &val);
-	if (ret || val >= clusters)
+	if (ret || val >= clusters || (s64)val < 0)
 		return -EINVAL;
 
 	atomic64_set(&sbi->s_resv_clusters, val);
@@ -451,7 +451,8 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
 						s_kobj);
 	struct ext4_attr *a = container_of(attr, struct ext4_attr, attr);
 	void *ptr = calc_ptr(a, sbi);
-	unsigned long t;
+	unsigned int t;
+	unsigned long lt;
 	int ret;
 
 	switch (a->attr_id) {
@@ -460,7 +461,7 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
 	case attr_pointer_ui:
 		if (!ptr)
 			return 0;
-		ret = kstrtoul(skip_spaces(buf), 0, &t);
+		ret = kstrtouint(skip_spaces(buf), 0, &t);
 		if (ret)
 			return ret;
 		if (a->attr_ptr == ptr_ext4_super_block_offset)
@@ -471,10 +472,10 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
 	case attr_pointer_ul:
 		if (!ptr)
 			return 0;
-		ret = kstrtoul(skip_spaces(buf), 0, &t);
+		ret = kstrtoul(skip_spaces(buf), 0, &lt);
 		if (ret)
 			return ret;
-		*((unsigned long *) ptr) = t;
+		*((unsigned long *) ptr) = lt;
 		return len;
 	case attr_inode_readahead:
 		return inode_readahead_blks_store(sbi, buf, len);
-- 
2.31.1