linux-kernel - Re: [PATCH] drm: etnaviv: fix strncpy sizeof argument

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Date:   Tue, 19 Mar 2019 19:09:06 +0800
From:   Bo YU <tsu.yubo@...il.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     l.stach@...gutronix.de,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        airlied@...ux.ie, Daniel Vetter <daniel@...ll.ch>,
        etnaviv@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        open list <linux-kernel@...r.kernel.org>,
        于波 <yuzibode@....com>
Subject: Re: [PATCH] drm: etnaviv: fix strncpy sizeof argument

On Tue, Mar 19, 2019 at 6:22 PM Russell King - ARM Linux admin
<linux@...linux.org.uk> wrote:
>
> On Mon, Mar 18, 2019 at 10:57:55PM -0400, Bo YU wrote:
> > Calling strncpy with a maximum size argument of 64 bytes on destination
> > array "domain->name" of size 64 bytes might leave the destination string
> > unterminated.
> >
> > Detected by CoverityScan, CID# 1443992:  Memory - illegal accesses
> > (BUFFER_SIZE_WARNING)
> >
> > Fixes: 9e2c2e2730126 (drm/etnaviv: add infrastructure to query perf counter)
> > Signed-off-by: Bo YU <tsu.yubo@...il.com>
> > ---
> >  drivers/gpu/drm/etnaviv/etnaviv_perfmon.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c b/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> > index 4227a4006c34..08ca3c44be48 100644
> > --- a/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> > +++ b/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> > @@ -414,7 +414,7 @@ int etnaviv_pm_query_dom(struct etnaviv_gpu *gpu,
> >
> >       domain->id = domain->iter;
> >       domain->nr_signals = dom->nr_signals;
> > -     strncpy(domain->name, dom->name, sizeof(domain->name));
> > +     strncpy(domain->name, dom->name, sizeof(dom->name));
>
> This introduces an overflow bug if sizeof(dom->name) >
> sizeof(domain->name).  If both sizes are the same, then there is no
> effect.
Oops,It seems more worse than original code.
>
> strlcpy() would be a better replacement, it guarantees that the
> destination will be correctly terminated.
But there are too many strcpy like usage in kernel, Does it matter?
>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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