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b=H4sIAL34LmUC/x3NQQrCQAxG4auUrA1kKip6FXExZH41IDMlKVUpv buDy2/z3koBNwRdhpUci4W12pF2A+kz1wfYSjeNMu6TpBPH7FWnLxe3BR5cMfPbHC9EsFpo42z eWLnIWYscRPIR1HuT426f/+t627YfhUfv7HsAAAA= X-Developer-Key: i=justinstitt@google.com; a=ed25519; pk=tC3hNkJQTpNX/gLKxTNQKDmiQl6QjBNCGKJINqAdJsE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1697577149; l=2545; i=justinstitt@google.com; s=20230717; h=from:subject:message-id; bh=iByoXcEl+/fTj7qfxJpQSjCOu1SG80zw46SDN1JdAVA=; b=422phc1KfoxKuZOVw01uw/lgnVEOwbLB9bZNBj3xD+nmrWlmWo1VFxb4TdilgcB/yQ/FizVWk oopegqE63ZDB+soiysSjOYI6D+ByXbd4dx2ld1FM64ecTwR85Ll2K55 X-Mailer: b4 0.12.3 Message-ID: <20231017-strncpy-drivers-net-wireless-cisco-airo-c-v1-1-e34d5b3b7e37@google.com> Subject: [PATCH] airo: replace deprecated strncpy with strscpy_pad From: Justin Stitt To: Kalle Valo Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Justin Stitt X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Tue, 17 Oct 2023 14:12:37 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1780038666590158626 X-GMAIL-MSGID: 1780038666590158626 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). 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 --- 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 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;