linux-kernel - [ 26/48] udf: Avoid run away loop when partition table length is corrupted

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Message-Id: <20120709143120.461951078@decadent.org.uk>
Date:	Mon, 09 Jul 2012 15:31:42 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Jan Kara <jack@...e.cz>
Subject: [ 26/48] udf: Avoid run away loop when partition table length is corrupted

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@...e.cz>

commit adee11b2085bee90bd8f4f52123ffb07882d6256 upstream.

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@...e.cz>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/udf/super.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 9da6f4e..ce911f5 100644
--- 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 *)


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