linux-kernel - Re: [PATCH] gpu/drm: fix a -Wstringop-truncation warning

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Message-ID: <1567694459.5576.94.camel@lca.pw>
Date:   Thu, 05 Sep 2019 10:40:59 -0400
From:   Qian Cai <cai@....pw>
To:     daniel@...ll.ch
Cc:     maarten.lankhorst@...ux.intel.com, maxime.ripard@...tlin.com,
        sean@...rly.run, airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpu/drm: fix a -Wstringop-truncation warning

Ping. Please take a look at this trivial patch.

On Fri, 2019-08-23 at 14:37 -0400, Qian Cai wrote:
> In file included from ./include/linux/bitmap.h:9,
>                  from ./include/linux/cpumask.h:12,
>                  from ./arch/x86/include/asm/cpumask.h:5,
>                  from ./arch/x86/include/asm/msr.h:11,
>                  from ./arch/x86/include/asm/processor.h:21,
>                  from ./arch/x86/include/asm/cpufeature.h:5,
>                  from ./arch/x86/include/asm/thread_info.h:53,
>                  from ./include/linux/thread_info.h:38,
>                  from ./arch/x86/include/asm/preempt.h:7,
>                  from ./include/linux/preempt.h:78,
>                  from ./include/linux/rcupdate.h:27,
>                  from ./include/linux/rculist.h:11,
>                  from ./include/linux/pid.h:5,
>                  from ./include/linux/sched.h:14,
>                  from ./include/linux/uaccess.h:5,
>                  from drivers/gpu/drm/drm_property.c:24:
> In function 'strncpy',
>     inlined from 'drm_property_create' at
> drivers/gpu/drm/drm_property.c:130:2:
> ./include/linux/string.h:305:9: warning: '__builtin_strncpy' specified
> bound 32 equals destination size [-Wstringop-truncation]
>   return __builtin_strncpy(p, q, size);
>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Fix it by using strscpy() which will always return a valid string, and
> doesn't unnecessarily force the tail of the destination buffer to be
> zeroed.
> 
> Signed-off-by: Qian Cai <cai@....pw>
> ---
>  drivers/gpu/drm/drm_property.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_property.c b/drivers/gpu/drm/drm_property.c
> index 892ce636ef72..66ec2cc7a559 100644
> --- a/drivers/gpu/drm/drm_property.c
> +++ b/drivers/gpu/drm/drm_property.c
> @@ -127,8 +127,7 @@ struct drm_property *drm_property_create(struct drm_device
> *dev,
>  	property->num_values = num_values;
>  	INIT_LIST_HEAD(&property->enum_list);
>  
> -	strncpy(property->name, name, DRM_PROP_NAME_LEN);
> -	property->name[DRM_PROP_NAME_LEN-1] = '\0';
> +	strscpy(property->name, name, DRM_PROP_NAME_LEN);
>  
>  	list_add_tail(&property->head, &dev->mode_config.property_list);
>