[PATCH v2] xfs: Verify DA node btree hash order

[Charalampos Mitrodimas]

The xfs_da3_node_verify() function checks the integrity of directory
and attribute B-tree node blocks. However, it was missing a check to
ensure that the hash values of the btree entries within the node are
non-decreasing hash values (allowing equality).

Add a loop to iterate through the btree entries and verify that each
entry's hash value is greater than the previous one. If an
out-of-order hash value is detected, return failure to indicate
corruption.

This addresses the "XXX: hash order check?" comment and improves
corruption detection for DA node blocks.

Signed-off-by: Charalampos Mitrodimas <charmitro@xxxxxxxxxx>
---
Changes in v2:
- Changed comparison from <= to < to allow equal hash values.
- Updated commit message to clarify "non-decreasing" nature of hash
  values.
- Link to v1: https://lore.kernel.org/r/20250412-xfs-hash-check-v1-1-fec1fef5d006@xxxxxxxxxx
---
 fs/xfs/libxfs/xfs_da_btree.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
index 17d9e6154f1978ce5a5cb82176eea4d6b9cd768d..7c42be30c3eb746e12b457ca6fce7c88ac191ba8 100644
--- a/fs/xfs/libxfs/xfs_da_btree.c
+++ b/fs/xfs/libxfs/xfs_da_btree.c
@@ -247,7 +247,16 @@ xfs_da3_node_verify(
 	    ichdr.count > mp->m_attr_geo->node_ents)
 		return __this_address;
 
-	/* XXX: hash order check? */
+	/* Check hash order */
+	uint32_t prev_hash = be32_to_cpu(ichdr.btree[0].hashval);
+
+	for (int i = 1; i < ichdr.count; i++) {
+		uint32_t curr_hash = be32_to_cpu(ichdr.btree[i].hashval);
+
+		if (curr_hash < prev_hash)
+			return __this_address;
+		prev_hash = curr_hash;
+	}
 
 	return NULL;
 }

---
base-commit: ecd5d67ad602c2c12e8709762717112ef0958767
change-id: 20250412-xfs-hash-check-be7397881a2c

Best regards,
-- 
Charalampos Mitrodimas <charmitro@xxxxxxxxxx>