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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id ij15-20020a170902ab4f00b001c9c47d6cb9sm940689plb.99.2023.10.10.16.59.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Oct 2023 16:59:12 -0700 (PDT) Date: Tue, 10 Oct 2023 16:59:10 -0700 From: Kees Cook To: Justin Stitt Cc: Marcin Wojtas , Russell King , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] net: mvpp2: replace deprecated strncpy with strscpy Message-ID: <202310101658.8D498F16F@keescook> References: <20231010-strncpy-drivers-net-ethernet-marvell-mvpp2-mvpp2_main-c-v1-1-51be96ad0324@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231010-strncpy-drivers-net-ethernet-marvell-mvpp2-mvpp2_main-c-v1-1-51be96ad0324@google.com> X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Tue, Oct 10, 2023 at 09:24:42PM +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. > > We expect `irqname` to be NUL-terminated based on its use with > of_irq_get_byname() -> of_property_match_string() wherein it is used > with a format string and a `strcmp`: > | pr_debug("comparing %s with %s\n", string, p); > | if (strcmp(string, p) == 0) > | return i; /* Found it; return index */ > > NUL-padding is not required as is evident by other assignments to > `irqname` which do not NUL-pad: > | if (port->flags & MVPP2_F_DT_COMPAT) > | snprintf(irqname, sizeof(irqname), "tx-cpu%d", i); > | else > | snprintf(irqname, sizeof(irqname), "hif%d", i); > > Considering the above, a suitable replacement is `strscpy` [2] due to > the fact that it guarantees NUL-termination on the destination buffer > without unnecessarily NUL-padding. > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt Yup, direct replacement. Reviewed-by: Kees Cook -- Kees Cook