udf: Avoid overflow when session starts at large offset

When session starts beyond offset 2^31 the arithmetics in
udf_check_vsd() would overflow. Make sure the computation is done in
large enough type.

Reported-by: Cezary Sliwa <sliwa@ifpan.edu.pl>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 99cb81d0077f940a2492e8ec109d5531adfcc7e6..08bf097507f6dc5df6427a871050f888956b9243 100644 (file)
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -703,7 +703,7 @@ static loff_t udf_check_vsd(struct super_block *sb)
        else
                sectorsize = sb->s_blocksize;
 
-       sector += (sbi->s_session << sb->s_blocksize_bits);
+       sector += (((loff_t)sbi->s_session) << sb->s_blocksize_bits);
 
        udf_debug("Starting at sector %u (%ld byte sectors)\n",
                  (unsigned int)(sector >> sb->s_blocksize_bits),