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

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Message-ID: <20190319102216.ylrkd6vxm77pq553@shell.armlinux.org.uk>
Date:   Tue, 19 Mar 2019 10:22:16 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Bo YU <tsu.yubo@...il.com>
Cc:     l.stach@...gutronix.de, christian.gmeiner@...il.com,
        airlied@...ux.ie, daniel@...ll.ch, etnaviv@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        yuzibode@....com
Subject: Re: [PATCH] drm: etnaviv: fix strncpy sizeof argument

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.

strlcpy() would be a better replacement, it guarantees that the
destination will be correctly terminated.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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