[PATCH 5/5] ocfs2: validate inline xattr header before reflinking inline xattrs

[ZhengYuan Huang <gality369@gmail.com>]

[BUG]
A corrupt inline xattr header can make ocfs2_reflink_xattr_inline() lock,
copy, and reflink xattr state from an unchecked ibody xattr header.

[CAUSE]
The inline reflink path still trusted di->i_xattr_inline_size to compute
header_off, xh, and new_xh before handing the source header to the reflink
allocator and copy logic.

[FIX]
Validate the source inode's inline xattr header with the shared helper
first, then derive the reflink copy offsets from the validated inline
size/header. This keeps the reflink path from traversing corrupt ibody
xattr geometry.

Signed-off-by: ZhengYuan Huang <gality369@gmail.com>
---
 fs/ocfs2/xattr.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 4877406a83ce..fcddd3c13acd 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -6511,12 +6511,10 @@ static int ocfs2_reflink_xattr_inline(struct ocfs2_xattr_reflink *args)
 	handle_t *handle;
 	struct ocfs2_super *osb = OCFS2_SB(args->old_inode->i_sb);
 	struct ocfs2_dinode *di = (struct ocfs2_dinode *)args->old_bh->b_data;
-	int inline_size = le16_to_cpu(di->i_xattr_inline_size);
-	int header_off = osb->sb->s_blocksize - inline_size;
-	struct ocfs2_xattr_header *xh = (struct ocfs2_xattr_header *)
-					(args->old_bh->b_data + header_off);
-	struct ocfs2_xattr_header *new_xh = (struct ocfs2_xattr_header *)
-					(args->new_bh->b_data + header_off);
+	int inline_size;
+	int header_off;
+	struct ocfs2_xattr_header *xh;
+	struct ocfs2_xattr_header *new_xh;
 	struct ocfs2_alloc_context *meta_ac = NULL;
 	struct ocfs2_inode_info *new_oi;
 	struct ocfs2_dinode *new_di;
@@ -6525,6 +6523,15 @@ static int ocfs2_reflink_xattr_inline(struct ocfs2_xattr_reflink *args)
 		.vb_access = ocfs2_journal_access_di,
 	};
 
+	ret = ocfs2_xattr_ibody_lookup_header(args->old_inode, di, &xh);
+	if (ret)
+		goto out;
+
+	inline_size = le16_to_cpu(di->i_xattr_inline_size);
+	header_off = osb->sb->s_blocksize - inline_size;
+	new_xh = (struct ocfs2_xattr_header *)
+		(args->new_bh->b_data + header_off);
+
 	ret = ocfs2_reflink_lock_xattr_allocators(osb, xh, args->ref_root_bh,
 						  &credits, &meta_ac);
 	if (ret) {
-- 
2.43.0