[Linux-kernel-mentees] [PATCH] media/v4l2-core: Fix kernel-infoleak in video_put_user()

[Peilin Ye]

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

Reported-and-tested-by: syzbot+79d751604cb6f29fbf59@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?extid=79d751604cb6f29fbf59
Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
---
 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