netdev - Re: KMSAN: uninit-value in __dev_mc

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Date:   Thu, 27 Sep 2018 23:30:26 +0200
From:   Vladis Dronov <vdronov@...hat.com>
To:     syzbot+001516d86dbe88862cec@...kaller.appspotmail.com,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: KMSAN: uninit-value in __dev_mc_add

Hello,

This report is actually for the same bug which was reported in:

https://syzkaller.appspot.com/bug?id=088efeac32fdde781038a777a63e436c0d4d7036

The note there that the bug was fixed by "Commits: net: fix uninit-value in
__hw_addr_add_ex()" is wrong. A C-reproducer from the 2nd syzkaller report
can trigger the bug from this one.

I've researched this and a result is a proposed patch, the problem is the tun
device code allowing to set an arbitrary link type.

https://lkml.org/lkml/2018/9/26/416
https://lore.kernel.org/lkml/20180926093018.6646-1-vdronov@redhat.com/T/#u
https://marc.info/?l=linux-netdev&m=153795423320016&w=2

A simplified reproducer is attached.

Best regards,
Vladis Dronov

View attachment "kmsan-hw_addr_add_ex.c" of type "text/plain" (2186 bytes)