linux-kernel - Re: [PATCH 03/64] rpmsg: glink: Replace strncpy() with strscpy

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Date:   Tue, 27 Jul 2021 21:07:45 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-hardening@...r.kernel.org,
        Keith Packard <keithpac@...zon.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH 03/64] rpmsg: glink: Replace strncpy() with strscpy_pad()

On Tue, Jul 27, 2021 at 01:57:54PM -0700, Kees Cook wrote:
> The use of strncpy() is considered deprecated for NUL-terminated
> strings[1]. Replace strncpy() with strscpy_pad() (as it seems this case
> expects the NUL padding to fill the allocation following the flexible
> array). This additionally silences a warning seen when building under
> -Warray-bounds:
> 
> ./include/linux/fortify-string.h:38:30: warning: '__builtin_strncpy' offset 24 from the object at '__mptr' is out of the bounds of referenced subobject 'data' with type 'u8[]' {aka 'unsigned char[]'} at offset 24 [-Warray-bounds]
>    38 | #define __underlying_strncpy __builtin_strncpy
>       |                              ^
> ./include/linux/fortify-string.h:50:9: note: in expansion of macro '__underlying_strncpy'
>    50 |  return __underlying_strncpy(p, q, size);
>       |         ^~~~~~~~~~~~~~~~~~~~
> drivers/rpmsg/qcom_glink_native.c: In function 'qcom_glink_work':
> drivers/rpmsg/qcom_glink_native.c:36:5: note: subobject 'data' declared here
>    36 |  u8 data[];
>       |     ^~~~
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks
--
Gustavo

> ---
>  drivers/rpmsg/qcom_glink_native.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index 05533c71b10e..c7b9de655080 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
> @@ -1440,7 +1440,7 @@ static int qcom_glink_rx_open(struct qcom_glink *glink, unsigned int rcid,
>  		}
>  
>  		rpdev->ept = &channel->ept;
> -		strncpy(rpdev->id.name, name, RPMSG_NAME_SIZE);
> +		strscpy_pad(rpdev->id.name, name, RPMSG_NAME_SIZE);
>  		rpdev->src = RPMSG_ADDR_ANY;
>  		rpdev->dst = RPMSG_ADDR_ANY;
>  		rpdev->ops = &glink_device_ops;
> -- 
> 2.30.2
>