netdev - Re: [PATCH net 3/3] wireguard: netlink: avoid variable-sized memcpy on sockaddr

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Message-ID: <202209160802.60021AF07@keescook>
Date:   Fri, 16 Sep 2022 08:04:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     kuba@...nel.org, pablo@...filter.org, davem@...emloft.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH net 3/3] wireguard: netlink: avoid variable-sized memcpy
 on sockaddr

On Fri, Sep 16, 2022 at 03:37:40PM +0100, Jason A. Donenfeld wrote:
> Doing a variable-sized memcpy is slower, and the compiler isn't smart
> enough to turn this into a constant-size assignment.
> 
> Further, Kees' latest fortified memcpy will actually bark, because the
> destination pointer is type sockaddr, not explicitly sockaddr_in or
> sockaddr_in6, so it thinks there's an overflow:
> 
>     memcpy: detected field-spanning write (size 28) of single field
>     "&endpoint.addr" at drivers/net/wireguard/netlink.c:446 (size 16)
> 
> Fix this by just assigning by using explicit casts for each checked
> case.
> 
> Cc: Kees Cook <keescook@...omium.org>
> Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>

Oh, also, please include reporter details:

Reported-by: syzbot+a448cda4dba2dac50de5@...kaller.appspotmail.com


-- 
Kees Cook