netdev - Re: [PATCH] net: can: prevent potential access of uninitialized value in canfd

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Message-ID: <28167915-ffeb-3555-7b7c-b735799b7831@pengutronix.de>
Date:   Mon, 2 Nov 2020 09:28:34 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Anant Thazhemadam <anant.thazhemadam@...il.com>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        syzbot+9bcb0c9409066696d3aa@...kaller.appspotmail.com
Subject: Re: [PATCH] net: can: prevent potential access of uninitialized value
 in canfd_rcv()

On 11/2/20 8:44 AM, Anant Thazhemadam wrote:
> 
> On 02-11-2020 12:40, Marc Kleine-Budde wrote:
>> On 11/2/20 4:13 AM, Anant Thazhemadam wrote:
>>> In canfd_rcv(), cfd->len is uninitialized when skb->len = 0, and this
>>> uninitialized cfd->len is accessed nonetheless by pr_warn_once().
>>>
>>> Fix this uninitialized variable access by checking cfd->len's validity
>>> condition (cfd->len > CANFD_MAX_DLEN) separately after the skb->len's
>>> condition is checked, and appropriately modify the log messages that
>>> are generated as well.
>>> In case either of the required conditions fail, the skb is freed and
>>> NET_RX_DROP is returned, same as before.
>>>
>>> Reported-by: syzbot+9bcb0c9409066696d3aa@...kaller.appspotmail.com
>>> Tested-by: Anant Thazhemadam <anant.thazhemadam@...il.com>
>>> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@...il.com>
>>> ---
>>> This patch was locally tested using the reproducer and .config file 
>>> generated by syzbot.
>>>
>>>  net/can/af_can.c | 19 ++++++++++++++-----
>>>  1 file changed, 14 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/net/can/af_can.c b/net/can/af_can.c
>>> index ea29a6d97ef5..1b9f2e50f065 100644
>>> --- a/net/can/af_can.c
>>> +++ b/net/can/af_can.c
>>> @@ -694,16 +694,25 @@ static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
>> Can you create a similar patch for "can_rcv()"?
> 
> Yes, I can. Would it be alright if that was part of the v2 itself (since it's similar changes)?
> Or would I have to split them up into 2 different patches and send it as a 2-patch series
> (since the changes made are in different functions)?

Please make it two patches. Please add a "Fixes" line to both patches.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
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