[PATCH v2] fs/ntfs3: Fix infinite loop in hdr_find_split due to zero-sized entry

[Jiasheng Jiang <jiashengjiangcool@gmail.com>]

The function hdr_find_split iterates over index entries to calculate a
split point. The loop increments the offset 'o' by 'esize', which is
derived directly from the on-disk 'e->size' field.

If a corrupted or malicious filesystem image contains an index entry
with a size of 0, the variable 'o' will fail to advance. This results
in an infinite loop if the condition 'o < used_2' remains true, causing
a kernel hang (Denial of Service).

This patch adds a sanity check to ensure 'esize' is at least the size
of the NTFS_DE structure, consistent with validation logic in sibling
functions like hdr_find_e.

Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
Signed-off-by: Jiasheng Jiang <jiashengjiangcool@gmail.com>
---
Changelog:

v1 -> v2:

1. Add a Fixes tag.
---
 fs/ntfs3/index.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ntfs3/index.c b/fs/ntfs3/index.c
index 7157cfd70fdc..da6927e6d360 100644
--- a/fs/ntfs3/index.c
+++ b/fs/ntfs3/index.c
@@ -577,6 +577,9 @@ static const struct NTFS_DE *hdr_find_split(const struct INDEX_HDR *hdr)
 			return p;
 
 		esize = le16_to_cpu(e->size);
+
+		if (esize < sizeof(struct NTFS_DE))
+			return NULL;
 	}
 
 	return e;
-- 
2.25.1