linux-kernel - Re: [Linux-kernel-mentees] [PATCH v3] media/v4l2-core: Fix kernel-infoleak in video_put

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Message-ID: <20200727220456.GA328887@PWN>
Date:   Mon, 27 Jul 2020 18:04:56 -0400
From:   Peilin Ye <yepeilin.cs@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Vandana BN <bnvandana@...il.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Linux-kernel-mentees] [PATCH v3] media/v4l2-core: Fix
 kernel-infoleak in video_put_user()

On Mon, Jul 27, 2020 at 04:16:08PM +0300, Dan Carpenter wrote:
> drivers/char/hpet.c:675 hpet_ioctl() warn: check that 'info' doesn't leak information (struct has a hole after 'hi_timer')

This one seems like a false positive.

drivers/char/hpet.c:670:

	mutex_lock(&hpet_mutex);
	err = hpet_ioctl_common(file->private_data, cmd, arg, &info);
	mutex_unlock(&hpet_mutex);

	if ((cmd == HPET_INFO) && !err &&
	    (copy_to_user((void __user *)arg, &info, sizeof(info))))
		err = -EFAULT;

`info` is only being copied to userspace when `cmd` is `HPET_INFO`.
However, hpet_ioctl_common() is already doing memset() on `info` in
`case HPET_INFO`:

drivers/char/hpet.c:612:

	case HPET_INFO:
		{
			memset(info, 0, sizeof(*info));
			^^^^^^

Thank you,
Peilin Ye