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: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
Changes in v2:
- use IW_ESSID_MAX_SIZE (thanks Jeff, Kees)
- Link to v1: https://lore.kernel.org/r/20231017-strncpy-drivers-net-wireless-cisco-airo-c-v1-1-e34d5b3b7e37@google.com
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
drivers/net/wireless/cisco/airo.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/net/wireless/cisco/airo.c b/drivers/net/wireless/cisco/airo.c
index dbd13f7aa3e6..6a099642e854 100644
--- a/drivers/net/wireless/cisco/airo.c
+++ b/drivers/net/wireless/cisco/airo.c
@@ -6067,8 +6067,7 @@ static int airo_get_nick(struct net_device *dev,
struct airo_info *local = dev->ml_priv;
readConfigRid(local, 1);
- strncpy(extra, local->config.nodeName, 16);
- extra[16] = '\0';
+ strscpy_pad(extra, local->config.nodeName, IW_ESSID_MAX_SIZE);
dwrq->length = strlen(extra);
return 0;
---
base-commit: 58720809f52779dc0f08e53e54b014209d13eebb
change-id: 20231017-strncpy-drivers-net-wireless-cisco-airo-c-d09cd0500a6e
Best regards,
--
Justin Stitt <[email protected]>
Kees Cook <[email protected]> writes:
> On Thu, Oct 26, 2023 at 11:19:18PM +0000, 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: [email protected]
>> Signed-off-by: Justin Stitt <[email protected]>
>
> Looks good; thanks!
>
> Reviewed-by: Kees Cook <[email protected]>
BTW most likely next week this driver and a bunch of other ancient
drivers will removed:
https://patchwork.kernel.org/project/linux-wireless/list/?series=795639&state=*&order=date
So to avoid unnecessary work on already removed drivers I recommend
using wireless-next as the baseline for wireless patches. Though I'm
still planning to apply this patch in case we ever add the driver back
(I hope not).
--
https://patchwork.kernel.org/project/linux-wireless/list/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches