Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200823082042.20816-1-himadrispandya@gmail.com>
In-Reply-To: <20200823082042.20816-1-himadrispandya@gmail.com>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Sun, 23 Aug 2020 11:26:27 +0200
Message-ID: <CACT4Y+Y1TpqYowNXj+OTcQwH-7T4n6PtPPa4gDWkV-np5KhKAQ@mail.gmail.com>
Subject: Re: [PATCH] net: usb: Fix uninit-was-stored issue in asix_read_cmd()
To:     Himadri Pandya <himadrispandya@gmail.com>
Cc:     David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        USB list <linux-usb@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sun, Aug 23, 2020 at 10:21 AM Himadri Pandya
<himadrispandya@gmail.com> wrote:
>
> Initialize the buffer before passing it to usb_read_cmd() function(s) to
> fix the uninit-was-stored issue in asix_read_cmd().
>
> Fixes: KMSAN: kernel-infoleak in raw_ioctl
> Reported by: syzbot+a7e220df5a81d1ab400e@syzkaller.appspotmail.com
>
> Signed-off-by: Himadri Pandya <himadrispandya@gmail.com>
> ---
>  drivers/net/usb/asix_common.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
> index e39f41efda3e..a67ea1971b78 100644
> --- a/drivers/net/usb/asix_common.c
> +++ b/drivers/net/usb/asix_common.c
> @@ -17,6 +17,8 @@ int asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
>
>         BUG_ON(!dev);
>
> +       memset(data, 0, size);

Hi Himadri,

I think the proper fix is to check
usbnet_read_cmd/usbnet_read_cmd_nopm return value instead.
Memsetting data helps to fix the warning at hand, but the device did
not send these 0's and we use them as if the device did send them.

Perhaps we need a separate helper function (of a bool flag) that will
fail on incomplete reads. Maybe even in the common USB layer because I
think we've seen this type of bug lots of times and I guess there are
dozens more.


>         if (!in_pm)
>                 fn = usbnet_read_cmd;
>         else
> --
> 2.17.1
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/20200823082042.20816-1-himadrispandya%40gmail.com.