lkml.org 
[lkml]   [2021]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [Linuxarm] [PATCH v1] drm/nouveau/device: append a NUL-terminated character for the string which filled by strncpy()
From
Date

On 2021/2/26 9:01, Song Bao Hua (Barry Song) wrote:
>
>> -----Original Message-----
>> From: Luo Jiaxing [mailto:luojiaxing@huawei.com]
>> Sent: Friday, February 26, 2021 12:39 AM
>> To: nouveau@lists.freedesktop.org; dri-devel@lists.freedesktop.org;
>> bskeggs@redhat.com
>> Cc: linux-kernel@vger.kernel.org; linuxarm@openeuler.org; luojiaxing
>> <luojiaxing@huawei.com>
>> Subject: [Linuxarm] [PATCH v1] drm/nouveau/device: append a NUL-terminated
>> character for the string which filled by strncpy()
>>
>> Following warning is found when using W=1 to build kernel:
>>
>> In function ‘nvkm_udevice_info’,
>> inlined from ‘nvkm_udevice_mthd’ at
>> drivers/gpu/drm/nouveau/nvkm/engine/device/user.c:195:10:
>> drivers/gpu/drm/nouveau/nvkm/engine/device/user.c:164:2: warning: ‘strncpy’
>> specified bound 16 equals destination size [-Wstringop-truncation]
>> 164 | strncpy(args->v0.chip, device->chip->name, sizeof(args->v0.chip));
>> drivers/gpu/drm/nouveau/nvkm/engine/device/user.c:165:2: warning: ‘strncpy’
>> specified bound 64 equals destination size [-Wstringop-truncation]
>> 165 | strncpy(args->v0.name, device->name, sizeof(args->v0.name));
>>
>> The reason of this warning is strncpy() does not guarantee that the
>> destination buffer will be NUL terminated. If the length of source string
>> is bigger than number we set by third input parameter, only first [number]
>> of characters is copied to the destination, and no NUL-terminated is
>> automatically added. There are some potential risks.
>>
>> Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
>> ---
>> drivers/gpu/drm/nouveau/nvkm/engine/device/user.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c
>> b/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c
>> index fea9d8f..2a32fe0 100644
>> --- a/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c
>> +++ b/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c
>> @@ -161,8 +161,10 @@ nvkm_udevice_info(struct nvkm_udevice *udev, void *data,
>> u32 size)
>> if (imem && args->v0.ram_size > 0)
>> args->v0.ram_user = args->v0.ram_user - imem->reserved;
>>
>> - strncpy(args->v0.chip, device->chip->name, sizeof(args->v0.chip));
>> - strncpy(args->v0.name, device->name, sizeof(args->v0.name));
>> + strncpy(args->v0.chip, device->chip->name, sizeof(args->v0.chip) - 1);
>> + args->v0.chip[sizeof(args->v0.chip) - 1] = '\0';
>> + strncpy(args->v0.name, device->name, sizeof(args->v0.name) - 1);
>> + args->v0.name[sizeof(args->v0.name) - 1] = '\0';
>
> Isn't it better to use snprintf()?


yes, you are right,  snprintf() is better. Most of drivers use
snprintf() to format a string,

but still some examples in kernel that use it for copy.


I modify to code to the follow and I think it's the same with strncpy
but more safety

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c
b/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c
index fea9d8f..4bf65bb 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c
@@ -161,8 +161,8 @@ nvkm_udevice_info(struct nvkm_udevice *udev, void
*data, u32 size)
        if (imem && args->v0.ram_size > 0)
                args->v0.ram_user = args->v0.ram_user - imem->reserved;

-       strncpy(args->v0.chip, device->chip->name, sizeof(args->v0.chip));
-       strncpy(args->v0.name, device->name, sizeof(args->v0.name));
+       snprintf(args->v0.chip, sizeof(args->v0.chip), "%s",
device->chip->name);
+       snprintf(args->v0.name, sizeof(args->v0.name), "%s", device->name);

Thanks

Jiaxing

>
>> return 0;
>> }
>>
> Thanks
> Barry
>

\
 
 \ /
  Last update: 2021-02-27 10:23    [W:0.059 / U:0.284 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site