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

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Date:   Sat, 31 Jul 2021 17:57:39 +0200
From:   Len Baker <len.baker@....com>
To:     Robert Richter <rric@...nel.org>
Cc:     Len Baker <len.baker@....com>, Kees Cook <keescook@...omium.org>,
        Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        James Morse <james.morse@....com>,
        linux-hardening@...r.kernel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/edac/edac_mc: Remove all strcpy() uses

Hi,

On Tue, Jul 27, 2021 at 02:38:47PM +0200, Robert Richter wrote:
> On 25.07.21 18:29:54, Len Baker wrote:
> >  drivers/edac/edac_mc.c | 16 ++++++++--------
> >  1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> > index f6d462d0be2d..1286364f0e48 100644
> > --- a/drivers/edac/edac_mc.c
> > +++ b/drivers/edac/edac_mc.c
> > @@ -1027,6 +1027,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
> >  {
> >  	struct dimm_info *dimm;
> >  	char *p;
> > +	size_t p_size = 0;
>
> I would rather use a 'left' variable which is initialized with
> sizeof(e->label) close to there p = e->label is.

Ok.

> >  	int row = -1, chan = -1;
> >  	int pos[EDAC_MAX_LAYERS] = { top_layer, mid_layer, low_layer };
> >  	int i, n_labels = 0;
> > @@ -1113,12 +1114,11 @@ 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);
> > -			p += strlen(p);
> > +			const char *or = (p != e->label) ? OTHER_LABEL : "";
> > +
> > +			p_size += scnprintf(p + p_size,
> > +					    sizeof(e->label) - p_size,
> > +					    "%s%s", or, dimm->label);
>
> My preference is to advance p here (and decrement 'left'). This is the
> pattern how p is used throughout the code. I also don't see a benefit
> of using scnprintf() here compared to the previous implementation.

Ok, no problem. I will send a new version more close to the original. The
scnprintf() returns the number of bytes writes to the buffer, so it is not
necessary to use the strlen() function. But if you prefer the current
pattern I will have no objection.

Regards,
Len