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Re: [PATCH v2] airo: replace deprecated strncpy with strscpy_pad

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On 10/26/2023 4:19 PM, Justin Stitt wrote:
strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

`extra` is clearly supposed to be NUL-terminated which is evident by the
manual NUL-byte assignment as well as its immediate usage with strlen().

Moreover, let's NUL-pad since there is deliberate effort (48 instances)
made elsewhere to zero-out buffers in these getters and setters:
6050 | memset(local->config.nodeName, 0, sizeof(local->config.nodeName));
6130 | memset(local->config.rates, 0, 8);
6139 | memset(local->config.rates, 0, 8);
6414 | memset(key.key, 0, MAX_KEY_SIZE);
6497 | memset(extra, 0, 16);
(to be clear, strncpy also NUL-padded -- we are matching that behavior)

Considering the above, a suitable replacement is `strscpy_pad` due to
the fact that it guarantees both NUL-termination and NUL-padding on the
destination buffer.

We can also replace the hard-coded size of "16" to IW_ESSID_MAX_SIZE
because this function is a wext handler.

In wext-core.c we have:
static const struct iw_ioctl_description standard_ioctl[] = {
...
         [IW_IOCTL_IDX(SIOCGIWNICKN)] = {
                 .header_type    = IW_HEADER_TYPE_POINT,
                 .token_size     = 1,
                 .max_tokens     = IW_ESSID_MAX_SIZE,
         },

So the buffer size is (strangely) IW_ESSID_MAX_SIZE

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@xxxxxxxxxxxxxxx
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>

Reviewed-by: Jeff Johnson <quic_jjohnson@xxxxxxxxxxx>




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