On 10/17/2023 2:12 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.
Technically, we can now copy one less byte into `extra` as we cannot
determine the sizeof `extra` at compile time and the hard-coded value of
16 means that strscpy_pad() will automatically truncate and set the byte
at offset 15 to NUL. However, the current code manually sets a
NUL-byte at offset 16. If this is an issue, the solution is to change
the hard-coded magic number to 17 instead of 16. I didn't do this in
this patch because a hard-coded 17 seems bad (even more so than 16).
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 if you want to use
that for the buffer 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>
---
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..8cfb1de5933e 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, 16);
dwrq->length = strlen(extra);
return 0;
---
base-commit: 58720809f52779dc0f08e53e54b014209d13eebb
change-id: 20231017-strncpy-drivers-net-wireless-cisco-airo-c-d09cd0500a6e
Best regards,
--
Justin Stitt <justinstitt@xxxxxxxxxx>
