[PATCH 1/2] ocfs2: add bounds checking to ocfs2_xattr_find_entry()

[Ferry Meng <mengferry@linux.alibaba.com>]

Just add redundant (perhaps paranoia) checks to make sure it doesn't
stray beyond valid meory region of ocfs2 xattr entry array during a
single match.

Maybe this patch can prevent some crash caused by crafted poison images.

Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
---
 fs/ocfs2/xattr.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 3b81213ed7b8..37be4a286faf 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -1062,8 +1062,8 @@ ssize_t ocfs2_listxattr(struct dentry *dentry,
 	return i_ret + b_ret;
 }
 
-static int ocfs2_xattr_find_entry(int name_index,
-				  const char *name,
+static int ocfs2_xattr_find_entry(struct inode *inode, void *end,
+				  int name_index, const char *name,
 				  struct ocfs2_xattr_search *xs)
 {
 	struct ocfs2_xattr_entry *entry;
@@ -1076,6 +1076,10 @@ static int ocfs2_xattr_find_entry(int name_index,
 	name_len = strlen(name);
 	entry = xs->here;
 	for (i = 0; i < le16_to_cpu(xs->header->xh_count); i++) {
+		if ((void *)entry >= end) {
+			ocfs2_error(inode->i_sb, "corrupted xattr entries");
+			return -EFSCORRUPTED;
+		}
 		cmp = name_index - ocfs2_xattr_get_type(entry);
 		if (!cmp)
 			cmp = name_len - entry->xe_name_len;
@@ -1166,7 +1170,7 @@ static int ocfs2_xattr_ibody_get(struct inode *inode,
 	xs->base = (void *)xs->header;
 	xs->here = xs->header->xh_entries;
 
-	ret = ocfs2_xattr_find_entry(name_index, name, xs);
+	ret = ocfs2_xattr_find_entry(inode, xs->end, name_index, name, xs);
 	if (ret)
 		return ret;
 	size = le64_to_cpu(xs->here->xe_value_size);
@@ -2698,7 +2702,7 @@ static int ocfs2_xattr_ibody_find(struct inode *inode,
 
 	/* Find the named attribute. */
 	if (oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL) {
-		ret = ocfs2_xattr_find_entry(name_index, name, xs);
+		ret = ocfs2_xattr_find_entry(inode, xs->end, name_index, name, xs);
 		if (ret && ret != -ENODATA)
 			return ret;
 		xs->not_found = ret;
@@ -2833,7 +2837,7 @@ static int ocfs2_xattr_block_find(struct inode *inode,
 		xs->end = (void *)(blk_bh->b_data) + blk_bh->b_size;
 		xs->here = xs->header->xh_entries;
 
-		ret = ocfs2_xattr_find_entry(name_index, name, xs);
+		ret = ocfs2_xattr_find_entry(inode, xs->end, name_index, name, xs);
 	} else
 		ret = ocfs2_xattr_index_block_find(inode, blk_bh,
 						   name_index,
-- 
2.32.0.3.g01195cf9f