[PATCH 1/4] ocfs2: validate dx_root extent list fields during block read

[Joseph Qi <joseph.qi@linux.alibaba.com>]

Move the extent list l_count validation from ocfs2_dx_dir_lookup_rec()
into ocfs2_validate_dx_root(), so that corrupted on-disk fields are
caught early at block read time rather than during directory lookups.

Additionally, add a l_next_free_rec <= l_count check to prevent
out-of-bounds access when iterating over extent records.

Both checks are skipped for inline dx roots (OCFS2_DX_FLAG_INLINE),
which use dr_entries instead of dr_list.

Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
---
 fs/ocfs2/dir.c | 34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
index 1c8abf2c592c..82e720c8ba32 100644
--- a/fs/ocfs2/dir.c
+++ b/fs/ocfs2/dir.c
@@ -593,7 +593,7 @@ static int ocfs2_validate_dx_root(struct super_block *sb,
 		mlog(ML_ERROR,
 		     "Checksum failed for dir index root block %llu\n",
 		     (unsigned long long)bh->b_blocknr);
-		return ret;
+		goto bail;
 	}
 
 	if (!OCFS2_IS_VALID_DX_ROOT(dx_root)) {
@@ -601,8 +601,32 @@ static int ocfs2_validate_dx_root(struct super_block *sb,
 				  "Dir Index Root # %llu has bad signature %.*s\n",
 				  (unsigned long long)le64_to_cpu(dx_root->dr_blkno),
 				  7, dx_root->dr_signature);
+		goto bail;
+	}
+
+	if (!(dx_root->dr_flags & OCFS2_DX_FLAG_INLINE)) {
+		struct ocfs2_extent_list *el = &dx_root->dr_list;
+
+		if (le16_to_cpu(el->l_count) != ocfs2_extent_recs_per_dx_root(sb)) {
+			ret = ocfs2_error(sb,
+					  "Dir Index Root # %llu has invalid l_count %u (expected %u)\n",
+					  (unsigned long long)le64_to_cpu(dx_root->dr_blkno),
+					  le16_to_cpu(el->l_count),
+					  ocfs2_extent_recs_per_dx_root(sb));
+			goto bail;
+		}
+
+		if (le16_to_cpu(el->l_next_free_rec) > le16_to_cpu(el->l_count)) {
+			ret = ocfs2_error(sb,
+					  "Dir Index Root # %llu has invalid l_next_free_rec %u (l_count %u)\n",
+					  (unsigned long long)le64_to_cpu(dx_root->dr_blkno),
+					  le16_to_cpu(el->l_next_free_rec),
+					  le16_to_cpu(el->l_count));
+			goto bail;
+		}
 	}
 
+bail:
 	return ret;
 }
 
@@ -791,14 +815,6 @@ static int ocfs2_dx_dir_lookup_rec(struct inode *inode,
 	struct ocfs2_extent_block *eb;
 	struct ocfs2_extent_rec *rec = NULL;
 
-	if (le16_to_cpu(el->l_count) !=
-	    ocfs2_extent_recs_per_dx_root(inode->i_sb)) {
-		ret = ocfs2_error(inode->i_sb,
-				  "Inode %lu has invalid extent list length %u\n",
-				  inode->i_ino, le16_to_cpu(el->l_count));
-		goto out;
-	}
-
 	if (el->l_tree_depth) {
 		ret = ocfs2_find_leaf(INODE_CACHE(inode), el, major_hash,
 				      &eb_bh);
-- 
2.39.3