udf: Avoid run away loop when partition table length is corrupted

Check provided length of partition table so that (possibly maliciously)
corrupted partition table cannot cause accessing data beyond current buffer.

Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 9da6f4ee112c8b46044806002d29f49964313cc3..ce911f50b39d8de9c1e627c0aa1173d37c330341 100644 (file)
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -1225,6 +1225,7 @@ static int udf_load_logicalvol(struct super_block *sb, sector_t block,
        struct genericPartitionMap *gpm;
        uint16_t ident;
        struct buffer_head *bh;
+       unsigned int table_len;
        int ret = 0;
 
        bh = udf_read_tagged(sb, block, block, &ident);
@@ -1232,13 +1233,20 @@ static int udf_load_logicalvol(struct super_block *sb, sector_t block,
                return 1;
        BUG_ON(ident != TAG_IDENT_LVD);
        lvd = (struct logicalVolDesc *)bh->b_data;
+       table_len = le32_to_cpu(lvd->mapTableLength);
+       if (sizeof(*lvd) + table_len > sb->s_blocksize) {
+               udf_err(sb, "error loading logical volume descriptor: "
+                       "Partition table too long (%u > %lu)\n", table_len,
+                       sb->s_blocksize - sizeof(*lvd));
+               goto out_bh;
+       }
 
        ret = udf_sb_alloc_partition_maps(sb, le32_to_cpu(lvd->numPartitionMaps));
        if (ret)
                goto out_bh;
 
        for (i = 0, offset = 0;
-            i < sbi->s_partitions && offset < le32_to_cpu(lvd->mapTableLength);
+            i < sbi->s_partitions && offset < table_len;
             i++, offset += gpm->partitionMapLength) {
                struct udf_part_map *map = &sbi->s_partmaps[i];
                gpm = (struct genericPartitionMap *)