Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1754233AbcL0LWu (ORCPT <rfc822;w@1wt.eu>);
        Tue, 27 Dec 2016 06:22:50 -0500
Received: from mga04.intel.com ([192.55.52.120]:60589 "EHLO mga04.intel.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1753688AbcL0LWl (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 27 Dec 2016 06:22:41 -0500
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.33,416,1477983600"; 
   d="asc'?scan'208";a="802640446"
From: Felipe Balbi <balbi@kernel.org>
To: Alan Stern <stern@rowland.harvard.edu>,
        Andrey Konovalov <andreyknvl@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        David Sterba <dsterba@suse.com>,
        Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>,
        David Eccher <d.eccher@gmail.com>, Bin Liu <b-liu@ti.com>,
        Mathieu Laurendeau <mat.lau@laposte.net>,
        Binyamin Sharet <s.binyamin@gmail.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        linux-usb@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>, Kostya Serebryany <kcc@google.com>,
        syzkaller <syzkaller@googlegroups.com>
Subject: Re: net/gadget: slab-out-of-bounds write in dev_config
In-Reply-To: <Pine.LNX.4.44L0.1612061027320.1674-100000@iolanthe.rowland.org>
References: <Pine.LNX.4.44L0.1612061027320.1674-100000@iolanthe.rowland.org>
Date: Tue, 27 Dec 2016 13:21:02 +0200
Message-ID: <87o9zx1uu9.fsf@linux.intel.com>
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="=-=-=";
        micalg=pgp-sha256; protocol="application/pgp-signature"
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 4750
Lines: 113

--=-=-=
Content-Type: text/plain
Content-Transfer-Encoding: quoted-printable


Hi,

Alan Stern <stern@rowland.harvard.edu> writes:
> On Tue, 6 Dec 2016, Andrey Konovalov wrote:
>
>> Hi!
>>=20
>> I've got the following error report while running the syzkaller fuzzer.
>>=20
>> ep0_write() doesn't check the length, so a user can cause an
>> out-of-bounds with both size and data controlled.
>> There's a comment which says "IN DATA+STATUS caller makes len <=3D
>> wLength". While I'm not exactly sure what that means, the length seems
>> to be passed unmodified directly from dev_config().
>
> You're right about the comment being misleading.  It looks like=20
> somebody forgot to actually do the check.
>
>> This doesn't seem to be a critical security issue since gadgetfs can't
>> be mounted from a user namespace.
>>=20
>> On commit 3c49de52d5647cda8b42c4255cf8a29d1e22eff5 (Dec 2).
>>=20
>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>> BUG: KASAN: slab-out-of-bounds in dev_config+0x86f/0x1190 at addr
>> ffff88003c47e160
>> Write of size 65537 by task syz-executor0/6356
>> CPU: 3 PID: 6356 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #19
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/=
2011
>>  ffff88003c107ad8 ffffffff81f96aba ffffffff3dc11ef0 1ffff10007820eee
>>  ffffed0007820ee6 ffff88003dc11f00 0000000041b58ab3 ffffffff8598b4c8
>>  ffffffff81f96828 ffffffff813fb4a0 ffff88003b6eadc0 ffff88003c107738
>> Call Trace:
>>  [<     inline     >] __dump_stack lib/dump_stack.c:15
>>  [<ffffffff81f96aba>] dump_stack+0x292/0x398 lib/dump_stack.c:51
>>  [<ffffffff817e4dec>] kasan_object_err+0x1c/0x70 mm/kasan/report.c:159
>>  [<     inline     >] print_address_description mm/kasan/report.c:197
>>  [<ffffffff817e5080>] kasan_report_error+0x1f0/0x4e0 mm/kasan/report.c:2=
86
>>  [<ffffffff817e5705>] kasan_report+0x35/0x40 mm/kasan/report.c:306
>>  [<     inline     >] check_memory_region_inline mm/kasan/kasan.c:308
>>  [<ffffffff817e3fb9>] check_memory_region+0x139/0x190 mm/kasan/kasan.c:3=
15
>>  [<ffffffff817e4044>] kasan_check_write+0x14/0x20 mm/kasan/kasan.c:326
>>  [<     inline     >] copy_from_user arch/x86/include/asm/uaccess.h:689
>>  [<     inline     >] ep0_write drivers/usb/gadget/legacy/inode.c:1135
>>  [<ffffffff83228caf>] dev_config+0x86f/0x1190
>> drivers/usb/gadget/legacy/inode.c:1759
>>  [<ffffffff817fdd55>] __vfs_write+0x5d5/0x760 fs/read_write.c:510
>>  [<ffffffff817ff650>] vfs_write+0x170/0x4e0 fs/read_write.c:560
>>  [<     inline     >] SYSC_write fs/read_write.c:607
>>  [<ffffffff81803a5b>] SyS_write+0xfb/0x230 fs/read_write.c:599
>>  [<ffffffff84f47ec1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> How does this patch work out?
>
> Alan Stern
>
>
>
> Index: usb-4.x/drivers/usb/gadget/legacy/inode.c
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> --- usb-4.x.orig/drivers/usb/gadget/legacy/inode.c
> +++ usb-4.x/drivers/usb/gadget/legacy/inode.c
> @@ -1126,7 +1126,7 @@ ep0_write (struct file *fd, const char _
>  	/* data and/or status stage for control request */
>  	} else if (dev->state =3D=3D STATE_DEV_SETUP) {
>=20=20
> -		/* IN DATA+STATUS caller makes len <=3D wLength */
> +		len =3D min(len, (size_t) dev->setup_wLength);
>  		if (dev->setup_in) {
>  			retval =3D setup_req (dev->gadget->ep0, dev->req, len);
>  			if (retval =3D=3D 0) {
>

I already have a patch from Greg for this. See [1]

[1] https://git.kernel.org/cgit/linux/kernel/git/balbi/usb.git/commit/?id=
=3D230bc0cb8ff222d9f0fbbd93a80393140b39481f

=2D-=20
balbi

--=-=-=
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=E9X/
-----END PGP SIGNATURE-----
--=-=-=--