[PATCH V3] Fix buffer size warning for strcpy

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.

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

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.

Signed-off-by: Nigel Croxon <redacted>
---
 super-ddf.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/super-ddf.c b/super-ddf.c
index dc8e512..1771316 100644
--- a/super-ddf.c
+++ b/super-ddf.c

@@ -2637,9 +2637,13 @@ 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 = strlen(ve->name);
+		if (l > 16)
+			l = 16;
+		memcpy(ve->name, name, l);
+	}
 	ddf->virt->populated_vdes =
 		cpu_to_be16(be16_to_cpu(ddf->virt->populated_vdes)+1);
 

-- 
2.29.2

On 23.08.2021 16:35, 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.

Yeah, please ignore my comment to v2- the task here it remove error, not
to acknowledge it.

+		int l = strlen(ve->name);
+		if (l > 16)
+			l = 16;

I think that whole "if" statement can be replaced by:
strnlen(ve->name, sizeof(ve->name))

+		memcpy(ve->name, name, l);
+	}

Hello Nigel,
It current form it is not working. See my finding below.

On 23.08.2021 17:36, Tkaczyk, Mariusz wrote:

quoted

+        int l = strlen(ve->name);

i think that you want to use name instead of ve->name.
length of ve->name is zero after memset.

quoted

+        if (l > 16)
+            l = 16;

I think that whole "if" statement can be replaced by:
strnlen(ve->name, sizeof(ve->name))

I did a mistake here.
I want to suggest usage of:
l = strnlen(name, sizeof(ve->name));

quoted

+        memcpy(ve->name, name, l);
+    }

Thanks,
Mariusz