linux-hardening - Re: [PATCH v3] drivers/edac/edac

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Date:   Sun, 8 Aug 2021 13:26:17 +0200
From:   Len Baker <len.baker@....com>
To:     Joe Perches <joe@...ches.com>, Robert Richter <rric@...nel.org>
Cc:     Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        James Morse <james.morse@....com>,
        Len Baker <len.baker@....com>,
        Kees Cook <keescook@...omium.org>,
        linux-hardening@...r.kernel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] drivers/edac/edac_mc: Remove all strcpy() uses

Hi,

On Sat, Aug 07, 2021 at 10:09:35AM -0700, Joe Perches wrote:
> On Sat, 2021-08-07 at 17:59 +0200, Len Baker wrote:
> > strcpy() performs no bounds checking on the destination buffer. This
> > could result in linear overflows beyond the end of the buffer, leading
> > to all kinds of misbehaviors. The safe replacement is strscpy().
>
> Probably better to change the commit subject to something like
> what is generally used by the subsystem.
>
> Maybe:
> 	EDAC/mc: Convert strcpy to strscpy
> or
> 	EDAC/mc: Prefer strscpy over strcpy

Ok, no problem. I like the second one.

> and also:
>
> > diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> []
> > @@ -1113,11 +1115,11 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
> >  			p = e->label;
> >  			*p = '\0';
> >  		} else {
> > -			if (p != e->label) {
> > -				strcpy(p, OTHER_LABEL);
> > -				p += strlen(OTHER_LABEL);
> > -			}
> > -			strcpy(p, dimm->label);
> > +			const char *text = (p != e->label) ? OTHER_LABEL :
> > +				dimm->label;
> > +
> > +			strscpy(p, text, len);
> > +			len -= strlen(p);
> >  			p += strlen(p);
>
> Perhaps this should use scnprintf rather than strscpy
> Something like:
> 			n += scnprintf(buf + n, len - n, "%s",
> 				       p == e->label ? dim->label : OTHER_LABEL);
>
In the first version [1] the scnprintf was used but Robert Richter don't
see any benefit compared with the current implementation.

[1] https://lore.kernel.org/linux-hardening/20210725162954.9861-1-len.baker@gmx.com/

Regards,
Len