linux-kernel - Re: [Intel-wired-lan] [PATCH net-next v6 19/21] pfcp: always set pfcp metadata

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Date: Thu, 4 Apr 2024 12:12:38 +0200
From: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Kees Cook <keescook@...omium.org>, Yury Norov <yury.norov@...il.com>,
	Marcin Szycik <marcin.szycik@...ux.intel.com>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	linux-kernel@...r.kernel.org,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Eric Dumazet <edumazet@...gle.com>, Netdev <netdev@...r.kernel.org>,
	Alexander Potapenko <glider@...gle.com>,
	Simon Horman <horms@...nel.org>,
	nex.sw.ncis.osdt.itp.upstreaming@...el.com,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"David S . Miller" <davem@...emloft.net>
Subject: Re: [Intel-wired-lan] [PATCH net-next v6 19/21] pfcp: always set
 pfcp metadata

On Thu, Apr 04, 2024 at 11:56:29AM +0200, Arnd Bergmann wrote:
> On Thu, Apr 4, 2024, at 11:45, Michal Swiatkowski wrote:
> > On Wed, Apr 03, 2024 at 10:59:36PM +0200, Arnd Bergmann wrote:
> >> On Wed, Mar 27, 2024, at 16:23, Alexander Lobakin wrote:
> >> 
> >> The memcpy() in the ip_tunnel_info_opts_set() causes
> >> a string.h fortification warning, with at least gcc-13:
> >> 
> >>     In function 'fortify_memcpy_chk',
> >>         inlined from 'ip_tunnel_info_opts_set' at include/net/ip_tunnels.h:619:3,
> >>         inlined from 'pfcp_encap_recv' at drivers/net/pfcp.c:84:2:
> >>     include/linux/fortify-string.h:553:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
> >>       553 |                         __write_overflow_field(p_size_field, size);
> >> 
> >> As far as I can tell, the warning is caused by the
> >> ambiguity of the union, but what I noticed is that
> >> it also seems to copy a buffer to itself, as 'md'
> >> is initialized to tun_dst->u.tun_info as well.
> >> 
> >> Is this intentional?
> >
> > I used ip_tunnel_info_opts_set() to set options_len and flags.
> > You are right that it can and probably should be changed to:
> >
> > __set_bit(IP_TUNNEL_PFCP_OPT_BIT, tun_dst->u.tun_info.key.tun_flags);
> > tun_dst->u.tun_info.options_len = sizeof(*md);
> >
> > instead of copying the buffer. Thanks for pointing it.
> >
> > Should I sent a fix to the net or patch to the maintainer? Sorry, don't
> > know how this kind of situations are being solved.
> 
> I tend to just send fixes when I run into build problems like this,
> but since you already know what's going on, I think it's best if
> you send the fix as well, citing the warning I mention in the commit
> log, and explaining that the warning can be avoided by the simpler
> code but is otherwise a false-positive.
> 

Thanks, I will sent the fix ASAP.

Michal
>      Arnd