linux-hardening - RE: [PATCH] kobject: Replace strlcpy with strscpy

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Date:   Tue, 11 Jul 2023 08:14:30 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Azeem Shaikh' <azeemshaikh38@...il.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] kobject: Replace strlcpy with strscpy

From: Azeem Shaikh
> Sent: 10 July 2023 19:07
> 
> On Mon, Jul 10, 2023 at 9:13 AM David Laight <David.Laight@...lab.com> wrote:
> >
> > >       int len;
> > >
> > > -     len = strlcpy(&env->buf[env->buflen], subsystem, buffer_size);
> > > -     if (len >= buffer_size) {
> > > +     len = strscpy(&env->buf[env->buflen], subsystem, buffer_size);
> > > +     if (len < 0) {
> > >               pr_warn("init_uevent_argv: buffer size of %d too small, needed %d\n",
> > >                       buffer_size, len);
> > >               return -ENOMEM;
> >
> > The size in the error message is now wrong.
> 
> Thanks for catching this.
> 
> > It has to be said that mostly all the strings that get copied
> > in the kernel are '\0' terminated - so maybe it is all moot.
> > OTOH printing (at least some of) the string that didn't fit
> > is a lot more useful than its length.
> 
> How about printing out strlen(subsystem) along with the entire value
> of @subsystem? So that the warn reads:
> 
> pr_warn("init_uevent_argv: buffer size of %d too small for %s, needed
> %d\n", buffer_size, subsystem, strlen(subsystem));
> 
> Does that seem better?

Not with the justification for not using strlcpy() :-)

	David

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