linux-kernel - [PATCH] media: v4l2-core: Fix Oops in ioctl

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Message-ID: <20200108105929.7kxwf5rthxnhwbuh@kili.mountain>
Date:   Wed, 8 Jan 2020 13:59:30 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Arnd Bergmann <arnd@...db.de>
Cc:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Vandana BN <bnvandana@...il.com>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [PATCH] media: v4l2-core: Fix Oops in ioctl

Syzbot reported a crash in video_usercopy().  It turns out when we
broke video_get_user() into a separate function then we accidentally
moved it outside the if block so it tries to memset a user pointer.

Reported-by: syzbot+9240c422be249a8422bd@...kaller.appspotmail.com
Fixes: c8ef1a6076bf ("media: v4l2-core: split out data copy from video_usercopy")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
Not actually tested.  :(  Sorry.

 drivers/media/v4l2-core/v4l2-ioctl.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index b68ff06009cd..aaf83e254272 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -3205,12 +3205,12 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
 			parg = mbuf;
 		}
 
+		err = video_get_user((void __user *)arg, parg, orig_cmd,
+				     &always_copy);
+		if (err)
+			goto out;
 	}
 
-	err = video_get_user((void __user *)arg, parg, orig_cmd, &always_copy);
-	if (err)
-		goto out;
-
 	err = check_array_args(cmd, parg, &array_size, &user_ptr, &kernel_ptr);
 	if (err < 0)
 		goto out;
-- 
2.11.0