netdev - Re: [PATCH] mac80211_hwsim: correctly handle zero length frames

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Message-ID: <YNLiHJuD3GuDgbKR@anirudhrb.com>
Date:   Wed, 23 Jun 2021 12:56:20 +0530
From:   Anirudh Rayabharam <mail@...rudhrb.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        syzbot+b2645b5bf1512b81fa22@...kaller.appspotmail.com,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, mail@...rudhrb.com
Subject: Re: [PATCH] mac80211_hwsim: correctly handle zero length frames

On Fri, Jun 18, 2021 at 11:36:16AM +0200, Johannes Berg wrote:
> On Thu, 2021-06-10 at 21:49 +0530, Anirudh Rayabharam wrote:
> > syzbot, using KMSAN, has reported an uninit-value access in
> > hwsim_cloned_frame_received_nl(). This is happening because frame_data_len
> > is 0. The code doesn't detect this case and blindly tries to read the
> > frame's header.
> > 
> > Fix this by bailing out in case frame_data_len is 0.
> 
> This really seems quite pointless - you should bail out if the frame is
> too short for what we need to do, not just when it's 0.

That makes sense. Do you happen to know what the min length of a valid
frame is? There doesn't seem to be constant defined for that already.

	- Anirudh

> 
> johannes
>