linux-kernel - [PATCH v2] loop: fix setting arbitrarily large block size

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Message-Id: <20210626082406.348821-1-chouhan.shreyansh630@gmail.com>
Date:   Sat, 26 Jun 2021 13:54:06 +0530
From:   Shreyansh Chouhan <chouhan.shreyansh630@...il.com>
To:     axboe@...nel.dk, hch@...radead.org
Cc:     Shreyansh Chouhan <chouhan.shreyansh630@...il.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+cf89d662483d6a1a0790@...kaller.appspotmail.com
Subject: [PATCH v2] loop: fix setting arbitrarily large block size

loop_validate_block_size took an unsigned short argument. Passing an
argument with size greater than the size of unsigned short would cause
an overflow and could potentially render the upper bound check on the
block size useless, allowing to set an arbitrarily large block size.

Reported-by: syzbot+cf89d662483d6a1a0790@...kaller.appspotmail.com
Signed-off-by: Shreyansh Chouhan <chouhan.shreyansh630@...il.com>
---

Changes from v1: Fixed the spelling of reported-by tag. Fixed the
commit message.

 drivers/block/loop.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 9a758cf66507..635baff0dd66 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -236,7 +236,7 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
  * @bsize: size to validate
  */
 static int
-loop_validate_block_size(unsigned short bsize)
+loop_validate_block_size(unsigned long bsize)
 {
 	if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
 		return -EINVAL;
-- 
2.31.1