netdev - Re: [PATCH net-next] net: Use _K_SS_MAXSIZE instead of absolute value

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Date: Thu, 20 Jul 2023 02:29:35 -0700
From: Breno Leitao <leitao@...ian.org>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: alexander@...alicyn.com, ast@...nel.org, davem@...emloft.net,
	dhowells@...hat.com, edumazet@...gle.com, kernelxing@...cent.com,
	kuba@...nel.org, leit@...a.com, linux-kernel@...r.kernel.org,
	lucien.xin@...il.com, martin.lau@...nel.org, netdev@...r.kernel.org,
	pabeni@...hat.com
Subject: Re: [PATCH net-next] net: Use _K_SS_MAXSIZE instead of absolute value

On Wed, Jul 19, 2023 at 10:30:17AM -0700, Kuniyuki Iwashima wrote:
> From: Breno Leitao <leitao@...ian.org>
> Date: Wed, 19 Jul 2023 10:18:49 -0700
> > On Wed, Jul 19, 2023 at 10:04:45AM -0700, Kuniyuki Iwashima wrote:
> > > From: Breno Leitao <leitao@...ian.org>
> > > Date: Wed, 19 Jul 2023 01:44:12 -0700
> > > > Looking at sk_getsockopt function, it is unclear why 128 is a magical
> > > > number.
> > > > 
> > > > Use the proper macro, so it becomes clear to understand what the value
> > > > mean, and get a reference where it is coming from (user-exported API).
> > > > 
> > > > Signed-off-by: Breno Leitao <leitao@...ian.org>
> > > > ---
> > > >  net/core/sock.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/net/core/sock.c b/net/core/sock.c
> > > > index 9370fd50aa2c..58b6f00197d6 100644
> > > > --- a/net/core/sock.c
> > > > +++ b/net/core/sock.c
> > > > @@ -1815,7 +1815,7 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
> > > >  
> > > >  	case SO_PEERNAME:
> > > >  	{
> > > > -		char address[128];
> > > > +		char address[_K_SS_MAXSIZE];
> > > 
> > > I guess you saw a bug caught by the fortified memcpy(), but this
> > > doesn't fix it properly.
> > 
> > Not really, in fact. I was reading this code, and I found this
> > discussion a while ago, where I got the idea:
> > 
> > https://lore.kernel.org/lkml/20140930.005925.995989898229686123.davem@davemloft.net/
> 
> I got it, but I prefer using struct sockaddr_storage as done in
> other places.
> 
>   $ grep -rn sockaddr_storage net/
> 
> Also, there would be some situations where we must cast each
> family-specific address back to sockaddr_storage for fortified
> library.
> 
> Then, it makes more sense to use sockaddr_storage rather than
> _K_SS_MAXSIZE.

Agree, that is a better fix. Thanks for working on it!