[PATCH 2/2] udf: Avoid run away loop when partition table length is corrupted

[Steve Conklin]

From: Jan Kara <jack at suse.cz>

CVE-2012-3400

BugLink: http://bugs.launchpad.net/bugs/1024497

Backported with changes to error prints from upstream commit adee11b2085bee90bd8f4f52123ffb07882d6256

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 at suse.cz>
Signed-off-by: Steve Conklin <sconklin at canonical.com>
---
 fs/udf/super.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 4ea5ad8..0940837 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -1303,6 +1303,7 @@ 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);
@@ -1310,6 +1311,14 @@ 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_error(sb, __func__,
+		    "error loading logical volume descriptor: Partition table too long (%u > %lu)\n",
+		    table_len,
+		    sb->s_blocksize - sizeof(*lvd));
+		goto out_bh;
+	}
 
 	i = udf_sb_alloc_partition_maps(sb, le32_to_cpu(lvd->numPartitionMaps));
 	if (i != 0) {
@@ -1318,7 +1327,7 @@ static int udf_load_logicalvol(struct super_block *sb, sector_t block,
 	}
 
 	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 *)
-- 
1.7.9.5