Re: [PATCH V5] Fix buffer size warning for strcpy

["Tkaczyk, Mariusz" <mariusz.tkaczyk@linux.intel.com>]

On 25.08.2021 17:30, Nigel Croxon wrote:
> To meet requirements of Common Criteria certification vulnerability
> assessment. Static code analysis has been run and found the following
> error:
> buffer_size_warning: Calling "strncpy" with a maximum size
> argument of 16 bytes on destination array "ve->name" of
> size 16 bytes might leave the destination string unterminated.
> https://people.redhat.com/ncroxon/mdadm-4.2-rc2-scan-results.html
> 
> The change is to make the destination size to fit the allocated size.
> 
> V5:
> Simplify the the strnlen call.
> 
> V4:
> Code cleanup of the interim "if" statement.
> 
> V3: Doc change only:
> The code change from filling ve->name with spaces to filling it with
> null-terminated is to comform to the SNIA - Common RAID Disk Data
> Format Specification. The format for VD_Name (ve->name) specifies
> the field to be either ASCII or UNICODE. Bit 2 of the VD_Type field
> MUST be used to determine the Unicode or ASCII format of this field.
> If this field is not used, all bytes MUST be set to zero.
> 
> V2: Change from zero-terminated to zero-padded on memset and
> change from using strncpy to memcpy, feedback from Neil Brown.
> 
> Tested-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>
> Signed-off-by: Nigel Croxon <ncroxon@redhat.com>
> ---
>   super-ddf.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/super-ddf.c b/super-ddf.c
> index dc8e512f..2eb617e6 100644
> --- a/super-ddf.c
> +++ b/super-ddf.c
> @@ -2637,9 +2637,11 @@ static int init_super_ddf_bvd(struct supertype *st,
>   		ve->init_state = DDF_init_not;
>   
>   	memset(ve->pad1, 0xff, 14);
> -	memset(ve->name, ' ', 16);
> -	if (name)
> -		strncpy(ve->name, name, 16);
> +	memset(ve->name, '\0', sizeof(ve->name));
> +	if (name) {
> +		int l = strnlen(name, sizeof(ve->name));
> +		memcpy(ve->name, name, l);
> +	}
>   	ddf->virt->populated_vdes =
>   		cpu_to_be16(be16_to_cpu(ddf->virt->populated_vdes)+1);
>   
> 

Reviewed-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>