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

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Date: Wed, 19 Jul 2023 10:18:49 -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 10:04:45AM -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/