loop: prevent information leak after failed read

If read was not fully successful we have to fail whole bio to prevent
information leak of old pages

##Testcase_begin
dd if=/dev/zero of=./file bs=1M count=1
losetup /dev/loop0 ./file -o 4096
truncate -s 0 ./file
# OOps loop offset is now beyond i_size, so read will silently fail.
# So bio's pages would not be cleared, may which result in information leak.
hexdump -C /dev/loop0
##testcase_end

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 3d80682..0d56739 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -372,7 +372,8 @@ do_lo_receive(struct loop_device *lo,
 
        if (retval < 0)
                return retval;
-
+       if (retval != bvec->bv_len)
+               return -EIO;
        return 0;
 }