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

From: Kees Cook <[email-masked]>
Date: Fri, 16 Sep 2022 08:04:01 -0700

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 <[email-masked]>
> Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
> Signed-off-by: Jason A. Donenfeld <[email-masked]>

Oh, also, please include reporter details:

Reported-by: [email-masked]

-- 
Kees Cook