[PATCH 1/2] ataflop: potential out of bounds in do_format()

From: Dan Carpenter <dan.carpenter@oracle.com>
To: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: [PATCH 1/2] ataflop: potential out of bounds in do_format()
Date: Wed, 21 Apr 2021 13:18:35 +0300	[thread overview]
Message-ID: <YH/7+65JruUO/wsg@mwanda> (raw)

The function uses "type" as an array index:

	q = unit[drive].disk[type]->queue;

Unfortunately the bounds check on "type" isn't done until later in the
function.  Fix this by moving the bounds check to the start.

Fixes: bf9c0538e485 ("ataflop: use a separate gendisk for each media format")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 drivers/block/ataflop.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index 104b713f4055..aed2c2a4f4ea 100644
--- a/drivers/block/ataflop.c
+++ b/drivers/block/ataflop.c
@@ -729,8 +729,12 @@ static int do_format(int drive, int type, struct atari_format_descr *desc)
 	unsigned long	flags;
 	int ret;
 
-	if (type)
+	if (type) {
 		type--;
+		if (type >= NUM_DISK_MINORS ||
+		    minor2disktype[type].drive_types > DriveType)
+			return -EINVAL;
+	}
 
 	q = unit[drive].disk[type]->queue;
 	blk_mq_freeze_queue(q);
@@ -742,11 +746,6 @@ static int do_format(int drive, int type, struct atari_format_descr *desc)
 	local_irq_restore(flags);
 
 	if (type) {
-		if (type >= NUM_DISK_MINORS ||
-		    minor2disktype[type].drive_types > DriveType) {
-			ret = -EINVAL;
-			goto out;
-		}
 		type = minor2disktype[type].index;
 		UDT = &atari_disk_type[type];
 	}
-- 
2.30.2

