linux-kernel - Re: [PATCH net-next] ipv4: ip_tunnel: Replace strcpy use with strscpy

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Message-ID: <9fab7b2389d43e0800024a431bd7736f22062f06.camel@aol.com>
Date: Thu, 01 May 2025 17:51:08 +0100
From: Ruben Wauters <rubenru09@....com>
To: Simon Horman <horms@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>, David Ahern
 <dsahern@...nel.org>,  Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] ipv4: ip_tunnel: Replace strcpy use with
 strscpy

On Thu, 2025-05-01 at 16:39 +0100, Simon Horman wrote:
> On Thu, May 01, 2025 at 02:23:00AM +0100, Ruben Wauters wrote:
> > Use of strcpy is decpreated, replaces the use of strcpy with
> > strscpy as
> > recommended.
> > 
> > I am aware there is an explicit bounds check above, however using
> > strscpy protects against buffer overflows in any future code, and
> > there
> > is no good reason I can see to not use it.
> 
> Thanks, I agree. This patch doesn't buy us safety. But it doesn't
> lose
> us anything. And allows the code to move towards best practice.
> 
> One thing I notices is that this change is is inconsistent with the
> call to
> the 3-argument variant of strscpy a few lines above - it should also
> be hte
> 2-argument version. Maybe that could be changed too. Maybe in a
> separate patch.


I can remove the size parameter from the above strscpy to make it
consistent in v2.

> It is customary when making such changes to add a note that
> strscpy() was chosen because the code expects a NUL-terminated string
> without zero-padding. (Which is the case due to the call to
> strcat().)
> Perhaps you could add some text to the commit message of v2 of this
> patch?

Apologies, I wasn't aware of this, I can add the text to v2.

Just a point of clarification I wanted to ask, for v2 of the patch,
should I include the Reviewed-by tag below? or should I remove it as
there has been changes?


> > Signed-off-by: Ruben Wauters <rubenru09@....com>
> 
> Reviewed-by: Simon Horman <horms@...nel.org>
> 
> > ---
> >  net/ipv4/ip_tunnel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
> > index 3913ec89ad20..9724bbbd0e0a 100644
> > --- a/net/ipv4/ip_tunnel.c
> > +++ b/net/ipv4/ip_tunnel.c
> > @@ -247,7 +247,7 @@ static struct net_device
> > *__ip_tunnel_create(struct net *net,
> >  	} else {
> >  		if (strlen(ops->kind) > (IFNAMSIZ - 3))
> >  			goto failed;
> > -		strcpy(name, ops->kind);
> > +		strscpy(name, ops->kind);
> >  		strcat(name, "%d");
> >  	}
> >  
> > -- 
> > 2.48.1
> > 
> > 
Ruben Wauters