linux-kernel - Re: KMSAN: kernel-infoleak in raw

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Message-ID: <20200810090833.GA2271719@kroah.com>
Date:   Mon, 10 Aug 2020 11:08:33 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot <syzbot+a7e220df5a81d1ab400e@...kaller.appspotmail.com>,
        Andrey Konovalov <andreyknvl@...gle.com>, balbi@...nel.org,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Alexander Potapenko <glider@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KMSAN: kernel-infoleak in raw_ioctl

On Mon, Aug 10, 2020 at 11:00:07AM +0200, Dmitry Vyukov wrote:
> On Mon, Aug 10, 2020 at 9:46 AM Greg KH <gregkh@...uxfoundation.org> wrote:
> >
> > On Sun, Aug 09, 2020 at 09:27:18AM -0700, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    ce8056d1 wip: changed copy_from_user where instrumented
> > > git tree:       https://github.com/google/kmsan.git master
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=141eb8b2900000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=3afe005fb99591f
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=a7e220df5a81d1ab400e
> > > compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> > > userspace arch: i386
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > The irony of a kernel module written for syzbot testing, causing syzbot
> > reports....
> 
> The raw gadget and KCOV are also kernel code and subject to all the
> same rules as any other kernel code from syzkaller point of view.
> 
> But I think the root cause of this bug is the origin of the uninitialized-ness:
> 
> Local variable ----buf.i@...x_get_phy_addr created at:
>  asix_read_cmd drivers/net/usb/asix_common.c:312 [inline]
>  asix_read_phy_addr drivers/net/usb/asix_common.c:295 [inline]
>  asix_get_phy_addr+0x4d/0x290 drivers/net/usb/asix_common.c:314
>  asix_read_cmd drivers/net/usb/asix_common.c:312 [inline]
>  asix_read_phy_addr drivers/net/usb/asix_common.c:295 [inline]
>  asix_get_phy_addr+0x4d/0x290 drivers/net/usb/asix_common.c:314

read buffers sent to USB hardware are ment to be filled in by the
hardware with the data received from it, we do not zero-out those
buffers before passing the pointer there.

Perhaps with testing frameworks like the raw usb controller, that might
cause a number of false-positives to happen?

thanks,

greg k-h