[PATCH 2/2] erofs-utils: avoid infinite loops due to corrupted subpage compact indexes

[Gao Xiang <hsiangkao@linux.alibaba.com>]

Source kernel commit: e13d315ae077bb7c3c6027cc292401bc0f4ec683

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 lib/zmap.c | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/lib/zmap.c b/lib/zmap.c
index 067e3ddd7cda..4a6507726ba8 100644
--- a/lib/zmap.c
+++ b/lib/zmap.c
@@ -60,10 +60,6 @@ static int z_erofs_load_full_lcluster(struct z_erofs_maprecorder *m,
 	} else {
 		m->partialref = !!(advise & Z_EROFS_LI_PARTIAL_REF);
 		m->clusterofs = le16_to_cpu(di->di_clusterofs);
-		if (m->clusterofs >= 1 << vi->z_lclusterbits) {
-			DBG_BUGON(1);
-			return -EFSCORRUPTED;
-		}
 		m->pblk = le32_to_cpu(di->di_u.blkaddr);
 	}
 	return 0;
@@ -246,14 +242,29 @@ static int z_erofs_load_compact_lcluster(struct z_erofs_maprecorder *m,
 static int z_erofs_load_lcluster_from_disk(struct z_erofs_maprecorder *m,
 					   unsigned int lcn, bool lookahead)
 {
-	switch (m->inode->datalayout) {
-	case EROFS_INODE_COMPRESSED_FULL:
-		return z_erofs_load_full_lcluster(m, lcn);
-	case EROFS_INODE_COMPRESSED_COMPACT:
-		return z_erofs_load_compact_lcluster(m, lcn, lookahead);
-	default:
-		return -EINVAL;
+	struct erofs_inode *vi = m->inode;
+	int err;
+
+	if (vi->datalayout == EROFS_INODE_COMPRESSED_COMPACT) {
+		err = z_erofs_load_compact_lcluster(m, lcn, lookahead);
+	} else {
+		DBG_BUGON(vi->datalayout != EROFS_INODE_COMPRESSED_FULL);
+		err = z_erofs_load_full_lcluster(m, lcn);
 	}
+	if (err)
+		return err;
+
+	if (m->type >= Z_EROFS_LCLUSTER_TYPE_MAX) {
+		erofs_err("unknown type %u @ lcn %u of nid %llu",
+			  m->type, lcn, m->inode->nid);
+		DBG_BUGON(1);
+		return -EOPNOTSUPP;
+	} else if (m->type != Z_EROFS_LCLUSTER_TYPE_NONHEAD &&
+		   m->clusterofs >= (1 << vi->z_lclusterbits)) {
+		DBG_BUGON(1);
+		return -EFSCORRUPTED;
+	}
+	return 0;
 }
 
 static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m,
-- 
2.43.5