[PATCH] fs/ntfs3: Fix OOB read in indx_insert_into_buffer

[Peng Zhang]

From: ZhangPeng <zhangpeng362@xxxxxxxxxx>

Syzbot reported a OOB read bug:

BUG: KASAN: slab-out-of-bounds in indx_insert_into_buffer+0xaa3/0x13b0
fs/ntfs3/index.c:1755
Read of size 17168 at addr ffff8880255e06c0 by task syz-executor308/3630

Call Trace:
 <TASK>
 memmove+0x25/0x60 mm/kasan/shadow.c:54
 indx_insert_into_buffer+0xaa3/0x13b0 fs/ntfs3/index.c:1755
 indx_insert_entry+0x446/0x6b0 fs/ntfs3/index.c:1863
 ntfs_create_inode+0x1d3f/0x35c0 fs/ntfs3/inode.c:1548
 ntfs_create+0x3e/0x60 fs/ntfs3/namei.c:100
 lookup_open fs/namei.c:3413 [inline]

If the member struct INDEX_BUFFER *index of struct indx_node is
incorrect, that is, the value of __le32 used is greater than the value
of __le32 total in struct INDEX_HDR. Therefore, OOB read occurs when
memmove is called in indx_insert_into_buffer().
Fix this by adding a check in hdr_find_e().

Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
Reported-by: syzbot+d882d57193079e379309@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: ZhangPeng <zhangpeng362@xxxxxxxxxx>
---
 fs/ntfs3/index.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ntfs3/index.c b/fs/ntfs3/index.c
index 440328147e7e..28af0a5afbf2 100644
--- a/fs/ntfs3/index.c
+++ b/fs/ntfs3/index.c
@@ -679,9 +679,13 @@ static struct NTFS_DE *hdr_find_e(const struct ntfs_index *indx,
 	u32 e_size, e_key_len;
 	u32 end = le32_to_cpu(hdr->used);
 	u32 off = le32_to_cpu(hdr->de_off);
+	u32 total = le32_to_cpu(hdr->total);
 	u16 offs[128];
 
 fill_table:
+	if (end > total)
+		return NULL;
+
 	if (off + sizeof(struct NTFS_DE) > end)
 		return NULL;
 
-- 
2.25.1