[PATCH v2 2/4] ntfs: centalize $INDEX_ROOT header validation

[Hyunchul Lee <hyc.lee@gmail.com>]

Add a dedicated helper to perform stricter validation of $INDEX_ROOT and
use it for both directory inodes and named index inodes. This keeps the
root size and header geometry checks consistent across both read paths.

Tested-by: woot000 <woot000@woot000.com>
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
---
 fs/ntfs/index.c | 18 ++++++++++++++++++
 fs/ntfs/index.h |  3 +++
 fs/ntfs/inode.c | 11 ++---------
 3 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/fs/ntfs/index.c b/fs/ntfs/index.c
index 9713b082b03d..97c0e7d6a580 100644
--- a/fs/ntfs/index.c
+++ b/fs/ntfs/index.c
@@ -541,6 +541,24 @@ int ntfs_index_block_inconsistent(struct ntfs_volume *vol,
 	return 0;
 }
 
+int ntfs_index_root_inconsistent(struct ntfs_volume *vol,
+				 const struct attr_record *a,
+				 const struct index_root *ir, u64 inum)
+{
+	u32 value_length = le32_to_cpu(a->data.resident.value_length);
+
+	if (value_length < offsetof(struct index_root, index)) {
+		ntfs_error(vol->sb, "$INDEX_ROOT in inode %llu is too small.",
+			   (unsigned long long)inum);
+		return -EIO;
+	}
+
+	return ntfs_index_header_inconsistent(vol, &ir->index,
+					      value_length -
+					      offsetof(struct index_root, index),
+					      inum);
+}
+
 static struct index_root *ntfs_ir_lookup(struct ntfs_inode *ni, __le16 *name,
 		u32 name_len, struct ntfs_attr_search_ctx **ctx)
 {
diff --git a/fs/ntfs/index.h b/fs/ntfs/index.h
index 3451ec8a1c4e..cad78568d8b3 100644
--- a/fs/ntfs/index.h
+++ b/fs/ntfs/index.h
@@ -89,6 +89,9 @@ struct ntfs_index_context {
 	bool sync_write;
 };
 
+int ntfs_index_root_inconsistent(struct ntfs_volume *vol,
+				 const struct attr_record *a,
+				 const struct index_root *ir, u64 inum);
 int ntfs_index_block_inconsistent(struct ntfs_volume *vol,
 				  const struct index_block *ib,
 				  u32 block_size, s64 vcn, u64 inum);
diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
index 360bebd1ee3f..63ee7acff4fc 100644
--- a/fs/ntfs/inode.c
+++ b/fs/ntfs/inode.c
@@ -890,7 +890,6 @@ static int ntfs_read_locked_inode(struct inode *vi)
 	 */
 	if (S_ISDIR(vi->i_mode)) {
 		struct index_root *ir;
-		u8 *ir_end, *index_end;
 
 view_index_meta:
 		/* It is a directory, find index root attribute. */
@@ -940,10 +939,7 @@ static int ntfs_read_locked_inode(struct inode *vi)
 		}
 		ir = (struct index_root *)((u8 *)a +
 				le16_to_cpu(a->data.resident.value_offset));
-		ir_end = (u8 *)ir + le32_to_cpu(a->data.resident.value_length);
-		index_end = (u8 *)&ir->index +
-				le32_to_cpu(ir->index.index_length);
-		if (index_end > ir_end) {
+		if (ntfs_index_root_inconsistent(ni->vol, a, ir, ni->mft_no)) {
 			ntfs_error(vi->i_sb, "Directory index is corrupt.");
 			goto unm_err_out;
 		}
@@ -1483,7 +1479,6 @@ static int ntfs_read_locked_index_inode(struct inode *base_vi, struct inode *vi)
 	struct attr_record *a;
 	struct ntfs_attr_search_ctx *ctx;
 	struct index_root *ir;
-	u8 *ir_end, *index_end;
 	int err = 0;
 
 	ntfs_debug("Entering for i_ino 0x%llx.", ni->mft_no);
@@ -1534,9 +1529,7 @@ static int ntfs_read_locked_index_inode(struct inode *base_vi, struct inode *vi)
 	}
 
 	ir = (struct index_root *)((u8 *)a + le16_to_cpu(a->data.resident.value_offset));
-	ir_end = (u8 *)ir + le32_to_cpu(a->data.resident.value_length);
-	index_end = (u8 *)&ir->index + le32_to_cpu(ir->index.index_length);
-	if (index_end > ir_end) {
+	if (ntfs_index_root_inconsistent(vol, a, ir, ni->mft_no)) {
 		ntfs_error(vi->i_sb, "Index is corrupt.");
 		goto unm_err_out;
 	}
-- 
2.43.0