udf: Fix crash during mount

Fix a crash during an attempt to mount a filesystem that has both
Unallocated Space Table and Unallocated Space Bitmap. Such filesystem
actually violates the UDF standard so we just have to properly detect
such situation and refuse to mount such filesystem read-write. When we
are at it, verify also other constraints on the allocation information
mandated by the standard.
Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/super.c

@@ -985,12 +985,62 @@ static struct udf_bitmap *udf_sb_alloc_bitmap(struct super_block *sb, u32 index)
 	return bitmap;
 }
 
+static int check_partition_desc(struct super_block *sb,
+				struct partitionDesc *p,
+				struct udf_part_map *map)
+{
+	bool umap, utable, fmap, ftable;
+	struct partitionHeaderDesc *phd;
+
+	switch (le32_to_cpu(p->accessType)) {
+	case PD_ACCESS_TYPE_READ_ONLY:
+	case PD_ACCESS_TYPE_WRITE_ONCE:
+	case PD_ACCESS_TYPE_REWRITABLE:
+	case PD_ACCESS_TYPE_NONE:
+		goto force_ro;
+	}
+
+	/* No Partition Header Descriptor? */
+	if (strcmp(p->partitionContents.ident, PD_PARTITION_CONTENTS_NSR02) &&
+	    strcmp(p->partitionContents.ident, PD_PARTITION_CONTENTS_NSR03))
+		goto force_ro;
+
+	phd = (struct partitionHeaderDesc *)p->partitionContentsUse;
+	utable = phd->unallocSpaceTable.extLength;
+	umap = phd->unallocSpaceBitmap.extLength;
+	ftable = phd->freedSpaceTable.extLength;
+	fmap = phd->freedSpaceBitmap.extLength;
+
+	/* No allocation info? */
+	if (!utable && !umap && !ftable && !fmap)
+		goto force_ro;
+
+	/* We don't support blocks that require erasing before overwrite */
+	if (ftable || fmap)
+		goto force_ro;
+	/* UDF 2.60: 2.3.3 - no mixing of tables & bitmaps, no VAT. */
+	if (utable && umap)
+		goto force_ro;
+
+	if (map->s_partition_type == UDF_VIRTUAL_MAP15 ||
+	    map->s_partition_type == UDF_VIRTUAL_MAP20)
+		goto force_ro;
+
+	return 0;
+force_ro:
+	if (!sb_rdonly(sb))
+		return -EACCES;
+	UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);
+	return 0;
+}
+
 static int udf_fill_partdesc_info(struct super_block *sb,
 		struct partitionDesc *p, int p_index)
 {
 	struct udf_part_map *map;
 	struct udf_sb_info *sbi = UDF_SB(sb);
 	struct partitionHeaderDesc *phd;
+	int err;
 
 	map = &sbi->s_partmaps[p_index];
 
@@ -1010,8 +1060,16 @@ static int udf_fill_partdesc_info(struct super_block *sb,
 		  p_index, map->s_partition_type,
 		  map->s_partition_root, map->s_partition_len);
 
-	if (strcmp(p->partitionContents.ident, PD_PARTITION_CONTENTS_NSR02) &&
-	    strcmp(p->partitionContents.ident, PD_PARTITION_CONTENTS_NSR03))
+	err = check_partition_desc(sb, p, map);
+	if (err)
+		return err;
+
+	/*
+	 * Skip loading allocation info it we cannot ever write to the fs.
+	 * This is a correctness thing as we may have decided to force ro mount
+	 * to avoid allocation info we don't support.
+	 */
+	if (UDF_QUERY_FLAG(sb, UDF_FLAG_RW_INCOMPAT))
 		return 0;
 
 	phd = (struct partitionHeaderDesc *)p->partitionContentsUse;
@@ -1047,9 +1105,6 @@ static int udf_fill_partdesc_info(struct super_block *sb,
 			  p_index, bitmap->s_extPosition);
 	}
 
-	if (phd->partitionIntegrityTable.extLength)
-		udf_debug("partitionIntegrityTable (part %d)\n", p_index);
-
 	if (phd->freedSpaceTable.extLength) {
 		struct kernel_lb_addr loc = {
 			.logicalBlockNum = le32_to_cpu(