[PATCH v2 1/2] xfs: reject log items with missing regions during recovery

[Weiming Shi <bestswngs@gmail.com>]

Each recovered log item is assembled in xlog_recover_add_to_trans() into
an ri_buf[] of ri_total (= the format's declared region count) slots, and
the regions actually logged are counted in ri_cnt. Nothing checks that
ri_cnt reached ri_total once the transaction is complete, so a crafted or
truncated log can present an item whose format declares more regions than
were logged. The trailing ri_buf[] slots are then NULL, and the reorder,
readahead and replay code dereference them.

For example, an XFS_LI_INODE item declaring two regions but logging only
the format region leaves ri_buf[1] NULL, and mount-time recovery faults
dereferencing it as the log dinode:

 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
 RIP: xlog_recover_inode_commit_pass2 (fs/xfs/xfs_inode_item_recover.c:370)
 Call Trace:
  xlog_recover_items_pass2 (fs/xfs/xfs_log_recover.c:2011)
  xlog_recover_commit_trans (fs/xfs/xfs_log_recover.c:2078)
  xlog_recovery_process_trans (fs/xfs/xfs_log_recover.c:2328)
  xlog_recover_process_data (fs/xfs/xfs_log_recover.c:2502)
  xlog_recover (fs/xfs/xfs_log_recover.c:3486)
  xfs_log_mount (fs/xfs/xfs_log.c:667)
  xfs_mountfs (fs/xfs/xfs_mount.c:1039)
  xfs_fs_fill_super (fs/xfs/xfs_super.c:1965)
  get_tree_bdev_flags (fs/super.c:1680)
  __x64_sys_mount (fs/namespace.c:4433)

Whether an item logged all its declared regions is a generic log format
property, not a per-item-type concern, so reject any item with a missing
region in xlog_recover_commit_trans() before the item ops run.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Xiang Mei <xmei5@asu.edu>
Suggested-by: Dave Chinner <dgc@kernel.org>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
---
 fs/xfs/xfs_log_recover.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 09e6678ca487..5250d512a392 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2039,6 +2039,17 @@ xlog_recover_commit_trans(
 
 	hlist_del_init(&trans->r_list);
 
+	/*
+	 * Reject an item missing a region its format declared; the NULL slot
+	 * would be dereferenced by the reorder and replay code.
+	 */
+	list_for_each_entry(item, &trans->r_itemq, ri_list) {
+		if (XFS_IS_CORRUPT(log->l_mp,
+				   item->ri_total == 0 ||
+				   item->ri_cnt != item->ri_total))
+			return -EFSCORRUPTED;
+	}
+
 	error = xlog_recover_reorder_trans(log, trans, pass);
 	if (error)
 		return error;
-- 
2.43.0