[PATCH 1/7] ext4: avoid overflow when setting values via sysfs

[Baokun Li]

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 when the value set is outside the variable type range, -EINVAL is
returned 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@xxxxxxxxxx>
---
 fs/ext4/sysfs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index 6d332dff79dd..3671a8aaf4af 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);
@@ -463,6 +463,8 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
 		ret = kstrtoul(skip_spaces(buf), 0, &t);
 		if (ret)
 			return ret;
+		if (t != (unsigned int)t)
+			return -EINVAL;
 		if (a->attr_ptr == ptr_ext4_super_block_offset)
 			*((__le32 *) ptr) = cpu_to_le32(t);
 		else
-- 
2.31.1