udf: Improve table length check to avoid possible overflow

commit 57b9655d01ef057a523e810d29c37ac09b80eead upstream.

When a partition table length is corrupted to be close to 1 << 32, the
check for its length may overflow on 32-bit systems and we will think
the length is valid. Later on the kernel can crash trying to read beyond
end of buffer. Fix the check to avoid possible overflow.

Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 988a332e30ddb5a65c9c6a3f67ead875f818355f..1d36fdd4ae56e0100660e126c1a6bf235bf10236 100644 (file)
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -1307,7 +1307,7 @@ static int udf_load_logicalvol(struct super_block *sb, sector_t block,
        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) {
+       if (table_len > sb->s_blocksize - sizeof(*lvd)) {
                udf_error(sb, "error loading logical volume descriptor: "
                          "Partition table too long (%u > %lu)\n", table_len,
                          sb->s_blocksize - sizeof(*lvd));