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

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Date:   Fri, 18 Jun 2021 11:36:16 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Anirudh Rayabharam <mail@...rudhrb.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     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
Subject: Re: [PATCH] mac80211_hwsim: correctly handle zero length frames

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.

johannes