Merge tag 'erofs-for-6.18-rc3-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs

Pull erofs fixes from Gao Xiang:
 "Just three small fixes to address fuzzed images in relatively new
  features, as reported by Robert.

   - Hardening against fuzzed encoded extents

   - Fix infinite loops due to crafted subpage compact indexes

   - Improve z_erofs_extent_lookback()"

* tag 'erofs-for-6.18-rc3-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  erofs: consolidate z_erofs_extent_lookback()
  erofs: avoid infinite loops due to corrupted subpage compact indexes
  erofs: fix crafted invalid cases for encoded extents

Author: torvalds

fs/erofs/zmap.c

@@ -55,10 +55,6 @@ 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;
@@ -240,21 +236,29 @@ 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)
 {
+	struct erofs_inode *vi = EROFS_I(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(m->inode->i_sb, "unknown type %u @ lcn %u of nid %llu",
-				m->type, lcn, EROFS_I(m->inode)->nid);
+			  m->type, lcn, EROFS_I(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;
 	}
-
-	switch (EROFS_I(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;
-	}
+	return 0;
 }
 
 static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m,
@@ -268,20 +272,19 @@ static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m,
 		unsigned long lcn = m->lcn - lookback_distance;
 		int err;
 
+		if (!lookback_distance)
+			break;
+
 		err = z_erofs_load_lcluster_from_disk(m, lcn, false);
 		if (err)
 			return err;
-
 		if (m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
 			lookback_distance = m->delta[0];
-			if (!lookback_distance)
-				break;
 			continue;
-		} else {
-			m->headtype = m->type;
-			m->map->m_la = (lcn << lclusterbits) | m->clusterofs;
-			return 0;
 		}
+		m->headtype = m->type;
+		m->map->m_la = (lcn << lclusterbits) | m->clusterofs;
+		return 0;
 	}
 	erofs_err(sb, "bogus lookback distance %u @ lcn %lu of nid %llu",
 		  lookback_distance, m->lcn, vi->nid);
@@ -431,13 +434,6 @@ static int z_erofs_map_blocks_fo(struct inode *inode,
 			end = inode->i_size;
 	} else {
 		if (m.type != Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
-			/* m.lcn should be >= 1 if endoff < m.clusterofs */
-			if (!m.lcn) {
-				erofs_err(sb, "invalid logical cluster 0 at nid %llu",
-					  vi->nid);
-				err = -EFSCORRUPTED;
-				goto unmap_out;
-			}
 			end = (m.lcn << lclusterbits) | m.clusterofs;
 			map->m_flags |= EROFS_MAP_FULL_MAPPED;
 			m.delta[0] = 1;
@@ -596,7 +592,7 @@ static int z_erofs_map_blocks_ext(struct inode *inode,
 			vi->z_fragmentoff = map->m_plen;
 			if (recsz > offsetof(struct z_erofs_extent, pstart_lo))
 				vi->z_fragmentoff |= map->m_pa << 32;
-		} else if (map->m_plen) {
+		} else if (map->m_plen & Z_EROFS_EXTENT_PLEN_MASK) {
 			map->m_flags |= EROFS_MAP_MAPPED |
 				EROFS_MAP_FULL_MAPPED | EROFS_MAP_ENCODED;
 			fmt = map->m_plen >> Z_EROFS_EXTENT_PLEN_FMT_BIT;
@@ -715,6 +711,7 @@ static int z_erofs_map_sanity_check(struct inode *inode,
 				    struct erofs_map_blocks *map)
 {
 	struct erofs_sb_info *sbi = EROFS_I_SB(inode);
+	u64 pend;
 
 	if (!(map->m_flags & EROFS_MAP_ENCODED))
 		return 0;
@@ -732,6 +729,10 @@ static int z_erofs_map_sanity_check(struct inode *inode,
 	if (unlikely(map->m_plen > Z_EROFS_PCLUSTER_MAX_SIZE ||
 		     map->m_llen > Z_EROFS_PCLUSTER_MAX_DSIZE))
 		return -EOPNOTSUPP;
+	/* Filesystems beyond 48-bit physical block addresses are invalid */
+	if (unlikely(check_add_overflow(map->m_pa, map->m_plen, &pend) ||
+		     (pend >> sbi->blkszbits) >= BIT_ULL(48)))
+		return -EFSCORRUPTED;
 	return 0;
 }