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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id h10-20020a056a00000a00b00688435a9915sm8177865pfk.189.2023.10.24.16.46.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Oct 2023 16:46:05 -0700 (PDT) Date: Tue, 24 Oct 2023 16:46:04 -0700 From: Kees Cook To: Justin Stitt Cc: Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] s390/sclp: replace deprecated strncpy with strtomem Message-ID: <202310241645.62B11FE65@keescook> References: <20231023-strncpy-drivers-s390-char-sclp-c-v1-1-eaeef80522bb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231023-strncpy-drivers-s390-char-sclp-c-v1-1-eaeef80522bb@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 23, 2023 at 07:14:49PM +0000, Justin Stitt wrote: > Let's move away from using strncpy() as it is deprecated [1]. > > Instead use strtomem() as `e.id` is already marked as nonstring: > | char id[4] __nonstring; I'm surprised the compiler didn't complain about this -- I thought that was the point of the __nonstring attribute: to diagnose when used with a string function. Hmpf. > > We don't need strtomem_pad() because `e` is already memset to 0 -- > rendering any additional NUL-padding useless. > > 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/s390/char/sclp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/s390/char/sclp.c b/drivers/s390/char/sclp.c > index 8f74db689a0c..486cf57a1605 100644 > --- a/drivers/s390/char/sclp.c > +++ b/drivers/s390/char/sclp.c > @@ -81,7 +81,7 @@ static inline void sclp_trace(int prio, char *id, u32 a, u64 b, bool err) > struct sclp_trace_entry e; > > memset(&e, 0, sizeof(e)); > - strncpy(e.id, id, sizeof(e.id)); > + strtomem(e.id, id); Looks right to me; thanks! Reviewed-by: Kees Cook -Kees > e.a = a; > e.b = b; > debug_event(&sclp_debug, prio, &e, sizeof(e)); > > --- > base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c > change-id: 20231023-strncpy-drivers-s390-char-sclp-c-bb66226a7eaa > > Best regards, > -- > Justin Stitt > > -- Kees Cook