[net-next v2] pfcp: avoid copy warning by simplifing code

[net-next v2] pfcp: avoid copy warning by simplifing code

[Michal Swiatkowski]

From Arnd comments:
"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);"

It is a false-positivie caused by ambiguity of the union.

However, as Arnd noticed, copying here is unescessary. The code can be
simplified to avoid calling ip_tunnel_info_opts_set(), which is doing
copying, setting flags and options_len.

Set correct flags and options_len directly on tun_info.

Fixes: 6dd514f48110 ("pfcp: always set pfcp metadata")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/netdev/701f8f93-f5fb-408b-822a-37a1d5c424ba@app.fastmail.com/
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
---
v1 --> v2:
Links: https://lore.kernel.org/netdev/Zg6yMB%2F3w4EBQVDm@mev-dev/
 * Add Fixes and Closes tag
---
 drivers/net/pfcp.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/pfcp.c b/drivers/net/pfcp.c
index cc5b28c5f99f..69434fd13f96 100644
--- a/drivers/net/pfcp.c
+++ b/drivers/net/pfcp.c
@@ -80,9 +80,8 @@ static int pfcp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	else
 		pfcp_node_recv(pfcp, skb, md);
 
-	__set_bit(IP_TUNNEL_PFCP_OPT_BIT, flags);
-	ip_tunnel_info_opts_set(&tun_dst->u.tun_info, md, sizeof(*md),
-				flags);
+	__set_bit(IP_TUNNEL_PFCP_OPT_BIT, tun_dst->u.tun_info.key.tun_flags);
+	tun_dst->u.tun_info.options_len = sizeof(*md);
 
 	if (unlikely(iptunnel_pull_header(skb, PFCP_HLEN, skb->protocol,
 					  !net_eq(sock_net(sk),
-- 
2.42.0

Re: [net-next v2] pfcp: avoid copy warning by simplifing code

[Simon Horman]

On Fri, Apr 05, 2024 at 08:36:05AM +0200, Michal Swiatkowski wrote:
> >From Arnd comments:
> "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);"
> 
> It is a false-positivie caused by ambiguity of the union.
> 
> However, as Arnd noticed, copying here is unescessary. The code can be
> simplified to avoid calling ip_tunnel_info_opts_set(), which is doing
> copying, setting flags and options_len.
> 
> Set correct flags and options_len directly on tun_info.
> 
> Fixes: 6dd514f48110 ("pfcp: always set pfcp metadata")
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Closes: https://lore.kernel.org/netdev/701f8f93-f5fb-408b-822a-37a1d5c424ba@app.fastmail.com/
> Acked-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>

I agree that it's nice to avoid a copy.
But I do wonder where else this pattern may exist.
And if it might be worth introducing a helper for it.

Regardless, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

...

Re: [net-next v2] pfcp: avoid copy warning by simplifing code

[Michal Swiatkowski]

On Mon, Apr 08, 2024 at 09:18:29AM +0100, Simon Horman wrote:
> On Fri, Apr 05, 2024 at 08:36:05AM +0200, Michal Swiatkowski wrote:
> > >From Arnd comments:
> > "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);"
> > 
> > It is a false-positivie caused by ambiguity of the union.
> > 
> > However, as Arnd noticed, copying here is unescessary. The code can be
> > simplified to avoid calling ip_tunnel_info_opts_set(), which is doing
> > copying, setting flags and options_len.
> > 
> > Set correct flags and options_len directly on tun_info.
> > 
> > Fixes: 6dd514f48110 ("pfcp: always set pfcp metadata")
> > Reported-by: Arnd Bergmann <arnd@arndb.de>
> > Closes: https://lore.kernel.org/netdev/701f8f93-f5fb-408b-822a-37a1d5c424ba@app.fastmail.com/
> > Acked-by: Arnd Bergmann <arnd@arndb.de>
> > Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
> 
> I agree that it's nice to avoid a copy.
> But I do wonder where else this pattern may exist.
> And if it might be worth introducing a helper for it.

Right, the same is done in vxlan, ip_gre and ip6_gre at least. I will
send v3 with helper.

Thanks,
Michal

> 
> Regardless, this looks good to me.
> 
> Reviewed-by: Simon Horman <horms@kernel.org>
> 
> ...

Re: [net-next v2] pfcp: avoid copy warning by simplifing code

[Alexander Lobakin]

From: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Date: Mon, 8 Apr 2024 12:46:42 +0200

> On Mon, Apr 08, 2024 at 09:18:29AM +0100, Simon Horman wrote:
>> On Fri, Apr 05, 2024 at 08:36:05AM +0200, Michal Swiatkowski wrote:
>>> >From Arnd comments:
>>> "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);"
>>>
>>> It is a false-positivie caused by ambiguity of the union.
>>>
>>> However, as Arnd noticed, copying here is unescessary. The code can be
>>> simplified to avoid calling ip_tunnel_info_opts_set(), which is doing
>>> copying, setting flags and options_len.
>>>
>>> Set correct flags and options_len directly on tun_info.
>>>
>>> Fixes: 6dd514f48110 ("pfcp: always set pfcp metadata")
>>> Reported-by: Arnd Bergmann <arnd@arndb.de>
>>> Closes: https://lore.kernel.org/netdev/701f8f93-f5fb-408b-822a-37a1d5c424ba@app.fastmail.com/
>>> Acked-by: Arnd Bergmann <arnd@arndb.de>
>>> Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
>>
>> I agree that it's nice to avoid a copy.
>> But I do wonder where else this pattern may exist.
>> And if it might be worth introducing a helper for it.
> 
> Right, the same is done in vxlan, ip_gre and ip6_gre at least. I will
> send v3 with helper.

Dave applied v2 already, so send this helper as a general improvement
w/o "Fixes:" :D

> 
> Thanks,
> Michal
> 
>>
>> Regardless, this looks good to me.
>>
>> Reviewed-by: Simon Horman <horms@kernel.org>
>>
>> ...

Thanks,
Olek

Re: [net-next v2] pfcp: avoid copy warning by simplifing code

[Michal Swiatkowski]

On Mon, Apr 08, 2024 at 12:50:48PM +0200, Alexander Lobakin wrote:
> From: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
> Date: Mon, 8 Apr 2024 12:46:42 +0200
> 
> > On Mon, Apr 08, 2024 at 09:18:29AM +0100, Simon Horman wrote:
> >> On Fri, Apr 05, 2024 at 08:36:05AM +0200, Michal Swiatkowski wrote:
> >>> >From Arnd comments:
> >>> "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);"
> >>>
> >>> It is a false-positivie caused by ambiguity of the union.
> >>>
> >>> However, as Arnd noticed, copying here is unescessary. The code can be
> >>> simplified to avoid calling ip_tunnel_info_opts_set(), which is doing
> >>> copying, setting flags and options_len.
> >>>
> >>> Set correct flags and options_len directly on tun_info.
> >>>
> >>> Fixes: 6dd514f48110 ("pfcp: always set pfcp metadata")
> >>> Reported-by: Arnd Bergmann <arnd@arndb.de>
> >>> Closes: https://lore.kernel.org/netdev/701f8f93-f5fb-408b-822a-37a1d5c424ba@app.fastmail.com/
> >>> Acked-by: Arnd Bergmann <arnd@arndb.de>
> >>> Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
> >>
> >> I agree that it's nice to avoid a copy.
> >> But I do wonder where else this pattern may exist.
> >> And if it might be worth introducing a helper for it.
> > 
> > Right, the same is done in vxlan, ip_gre and ip6_gre at least. I will
> > send v3 with helper.
> 
> Dave applied v2 already, so send this helper as a general improvement
> w/o "Fixes:" :D
>

I missed that, thanks :) . So, I will send new patch.

> > 
> > Thanks,
> > Michal
> > 
> >>
> >> Regardless, this looks good to me.
> >>
> >> Reviewed-by: Simon Horman <horms@kernel.org>
> >>
> >> ...
> 
> Thanks,
> Olek

Re: [net-next v2] pfcp: avoid copy warning by simplifing code

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by David S. Miller <davem@davemloft.net>:

On Fri,  5 Apr 2024 08:36:05 +0200 you wrote:
> From Arnd comments:
> "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);"
> 
> [...]

Here is the summary with links:
  - [net-next,v2] pfcp: avoid copy warning by simplifing code
    https://git.kernel.org/netdev/net-next/c/cd8a34cbc853

You are awesome, thank you!
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