[PATCH] Fix buffer size warning for strcpy

[PATCH] Fix buffer size warning for strcpy

[Nigel Croxon]

To meet requirements of Common Criteria certification vulnerablility
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.

The change is to make the destination size to fit the allocated size.

Signed-off-by: Nigel Croxon <ncroxon@redhat.com>
---
 super-ddf.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/super-ddf.c b/super-ddf.c
index dc8e512f..486183ed 100644
--- a/super-ddf.c
+++ b/super-ddf.c
@@ -2637,9 +2637,10 @@ static int init_super_ddf_bvd(struct supertype *st,
 		ve->init_state = DDF_init_not;
 
 	memset(ve->pad1, 0xff, 14);
-	memset(ve->name, ' ', 16);
+	memset(ve->name, ' ', 15);
+	ve->name[15] = '\0';
 	if (name)
-		strncpy(ve->name, name, 16);
+		strncpy(ve->name, name, 15);
 	ddf->virt->populated_vdes =
 		cpu_to_be16(be16_to_cpu(ddf->virt->populated_vdes)+1);
 
-- 
2.29.2

Re: [PATCH] Fix buffer size warning for strcpy

[NeilBrown]

On Tue, 17 Aug 2021, Nigel Croxon wrote:
> To meet requirements of Common Criteria certification vulnerablility
> 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.
> 
> The change is to make the destination size to fit the allocated size.
> 
> Signed-off-by: Nigel Croxon <ncroxon@redhat.com>
> ---
>  super-ddf.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/super-ddf.c b/super-ddf.c
> index dc8e512f..486183ed 100644
> --- a/super-ddf.c
> +++ b/super-ddf.c
> @@ -2637,9 +2637,10 @@ static int init_super_ddf_bvd(struct supertype *st,
>  		ve->init_state = DDF_init_not;
>  
>  	memset(ve->pad1, 0xff, 14);
> -	memset(ve->name, ' ', 16);
> +	memset(ve->name, ' ', 15);
> +	ve->name[15] = '\0';
>  	if (name)
> -		strncpy(ve->name, name, 16);
> +		strncpy(ve->name, name, 15);

This is not correct.
ve->name is *not* required to be nul-terminated.  It is a string that
can be up to 16 bytes long.  If it is less than 16 bytes, it is
nul-padded.
Probably the way to get coverity to stop complaining is to use memcpy.
   if (name) {
      int l = strlen(name;
      if (l > 16)
           l = 16;
      memcpy(ve->name, name, l);
   }

Probably the ->name should be initialized to '\0', not spaces.

  https://www.snia.org/sites/default/files/SNIA_DDF_Technical_Position_v2.0.pdf

describes the format.  Some fields are specified as being padded with
spaces, but not VD_Name (which is ve->name).
The field is specified as being either ASCII or "UNICODE" (which doesn't
make any sense as "UNICODE" is not a byte-encoding.  Presumably it means
"UTF-8") and that:
    If this field is not used, all bytes MUST be set to zero.

So it should probably be zero-padded.  But there is definitely no
requirement for it to be zero-terminated.

Thanks,
NeilBrown


>  	ddf->virt->populated_vdes =
>  		cpu_to_be16(be16_to_cpu(ddf->virt->populated_vdes)+1);
>  
> -- 
> 2.29.2
> 
>