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

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Date:   Mon, 10 Jul 2023 14:06:44 -0400
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     David Laight <David.Laight@...lab.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

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?