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From:   Peilin Ye <yepeilin.cs@gmail.com>
To:     Mauro Carvalho Chehab <mchehab@kernel.org>
Cc:     Peilin Ye <yepeilin.cs@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        syzkaller-bugs@googlegroups.com,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Vandana BN <bnvandana@gmail.com>,
        Ezequiel Garcia <ezequiel@collabora.com>,
        =?UTF-8?q?Niklas=20S=C3=B6derlund?= 
        <niklas.soderlund+renesas@ragnatech.se>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [Linux-kernel-mentees] [PATCH] media/v4l2-core: Fix kernel-infoleak in video_put_user()
Date:   Sun, 26 Jul 2020 12:44:39 -0400
Message-Id: <20200726164439.48973-1-yepeilin.cs@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

video_put_user() is copying uninitialized stack memory to userspace. Fix
it by initializing `vb32` using memset().

Reported-and-tested-by: syzbot+79d751604cb6f29fbf59@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=79d751604cb6f29fbf59
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
 drivers/media/v4l2-core/v4l2-ioctl.c | 32 +++++++++++++++-------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index a556880f225a..08909f58dc80 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -3210,21 +3210,23 @@ static int video_put_user(void __user *arg, void *parg, unsigned int cmd)
 	case VIDIOC_DQBUF_TIME32:
 	case VIDIOC_PREPARE_BUF_TIME32: {
 		struct v4l2_buffer *vb = parg;
-		struct v4l2_buffer_time32 vb32 = {
-			.index		= vb->index,
-			.type		= vb->type,
-			.bytesused	= vb->bytesused,
-			.flags		= vb->flags,
-			.field		= vb->field,
-			.timestamp.tv_sec	= vb->timestamp.tv_sec,
-			.timestamp.tv_usec	= vb->timestamp.tv_usec,
-			.timecode	= vb->timecode,
-			.sequence	= vb->sequence,
-			.memory		= vb->memory,
-			.m.userptr	= vb->m.userptr,
-			.length		= vb->length,
-			.request_fd	= vb->request_fd,
-		};
+		struct v4l2_buffer_time32 vb32;
+
+		memset(&vb32, 0, sizeof(vb32));
+
+		vb32.index	= vb->index;
+		vb32.type	= vb->type;
+		vb32.bytesused	= vb->bytesused;
+		vb32.flags	= vb->flags;
+		vb32.field	= vb->field;
+		vb32.timestamp.tv_sec	= vb->timestamp.tv_sec;
+		vb32.timestamp.tv_usec	= vb->timestamp.tv_usec;
+		vb32.timecode	= vb->timecode;
+		vb32.sequence	= vb->sequence;
+		vb32.memory	= vb->memory;
+		vb32.m.userptr	= vb->m.userptr;
+		vb32.length	= vb->length;
+		vb32.request_fd	= vb->request_fd;
 
 		if (copy_to_user(arg, &vb32, sizeof(vb32)))
 			return -EFAULT;
-- 
2.25.1