| Message ID | 20231026-strncpy-drivers-net-wireless-cisco-airo-c-v2-1-413427249e47@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 9beac4ee49286101e30a1de2fe58625f998bf77c |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | [v2] airo: replace deprecated strncpy with strscpy_pad | expand |
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@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Kees Cook <keescook@chromium.org> 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: linux-hardening@vger.kernel.org >> Signed-off-by: Justin Stitt <justinstitt@google.com> > > Looks good; thanks! > > Reviewed-by: Kees Cook <keescook@chromium.org> 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).
Justin Stitt <justinstitt@google.com> 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@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> > Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com> Patch applied to wireless-next.git, thanks. 9beac4ee4928 wifi: airo: replace deprecated strncpy with strscpy_pad
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;
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@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> --- 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(-) --- base-commit: 58720809f52779dc0f08e53e54b014209d13eebb change-id: 20231017-strncpy-drivers-net-wireless-cisco-airo-c-d09cd0500a6e Best regards, -- Justin Stitt <justinstitt@google.com>