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b=AuDK154A5mN38XmZcqBSsdt7b45OCeP/L7FMPgXrQ2FJr8v8DrDZ+wtPSDG0e/7mo DHbexUmbSjjiD6EzwTJld7lOwk0OdS8oqtvH02Z9Ei9ydEMi1QaGGNr7dDR0FmLEb0 xwr3JwJjmOgbdryrcv5laspvHyIdVF++NqAKNCzOnq4CzgcT4oCrFOpduGVxCcZIiG eXF4H/OshyOQoeClRFpE9Vm/GsrqVnwelPulZehbpXDwQ3eKF1Y8dzsnUnzxgZ+nXy W0S2znRA9gAQn9rlR6kzbC7ak5ssSE8yIEqEL1rWP5AC9ETIN8qNVM5OzBnryiVO8p Z+0gqfx1fKD3w== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1qc3p8-009xKP-6M; Fri, 01 Sep 2023 14:04:30 +0100 Date: Fri, 01 Sep 2023 14:04:29 +0100 Message-ID: <86ttsedoyq.wl-maz@kernel.org> From: Marc Zyngier To: Mostafa Saleh , justinstitt@google.com Cc: catalin.marinas@arm.com, will@kernel.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, oliver.upton@linux.dev, kristina.martsenko@arm.com, broonie@kernel.org, quic_pkondeti@quicinc.com Subject: Re: [PATCH] Revert "arm64/sysreg: refactor deprecated strncpy" In-Reply-To: References: <20230831162227.2307863-1-smostafa@google.com> <86v8cudtky.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/28.2 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: smostafa@google.com, justinstitt@google.com, catalin.marinas@arm.com, will@kernel.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, oliver.upton@linux.dev, kristina.martsenko@arm.com, broonie@kernel.org, quic_pkondeti@quicinc.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230901_060438_054820_96446D0E X-CRM114-Status: GOOD ( 39.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 01 Sep 2023 12:57:10 +0100, Mostafa Saleh wrote: > > Hi Marc, > > On Fri, Sep 01, 2023 at 12:24:45PM +0100, Marc Zyngier wrote: > > Hi Mostafa, > > > > On Thu, 31 Aug 2023 17:22:27 +0100, > > Mostafa Saleh wrote: > > > > > > This reverts commit d232606773a0b09ec7f1ffc25f63abe801d011fd. > > > > > > Using strscpy is not correct in this context and the commit > > > assumption is not right "strncpy is deprecated for use on > > > NUL-terminated destination strings". > > > > > > strncpy is used here to copy parts of the string(cmdline) separated > > > by spaces into the buffer and not a NULL terminated string. > > > > > > This breaks the arm options "kvm-arm.mode=protected, arm64.nobti ..." > > > > > > Signed-off-by: Mostafa Saleh > > > --- > > > arch/arm64/kernel/idreg-override.c | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c > > > index aee12c75b738..2fe2491b692c 100644 > > > --- a/arch/arm64/kernel/idreg-override.c > > > +++ b/arch/arm64/kernel/idreg-override.c > > > @@ -262,9 +262,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) > > > if (!len) > > > return; > > > > > > - len = strscpy(buf, cmdline, ARRAY_SIZE(buf)); > > > - if (len == -E2BIG) > > > - len = ARRAY_SIZE(buf) - 1; > > > + len = min(len, ARRAY_SIZE(buf) - 1); > > > + strncpy(buf, cmdline, len); > > > + buf[len] = 0; > > > > > > if (strcmp(buf, "--") == 0) > > > return; > > > > Instead of completely reverting the patch, maybe something like the > > hack below (completely untested), so that we can still get rid of > > another instance of strncpy(), and yet bring back some sanity in the > > logic? > I was thinking of something similar, but I see we limit the len anyway > by the buffer size - 1 and force the NUL at the end so it should be > safe, unless the goal is to get rid of strncpy all the way, in this > case we can do it as you proposed. > > There is also a V3 of the original patch which uses memcpy instead. > https://lore.kernel.org/all/20230831-strncpy-arch-arm64-v3-1-cdbb1e7ea5e1@google.com/ Ah, that one would actually get my vote, because it does exactly what I actually intended this piece of code to do. Justin, do you mind rebasing your v3 on top of to restore the currently broken functionality? > > > Thanks, > > > > M. > > > > diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c > > index aee12c75b738..be5c778a3f14 100644 > > --- a/arch/arm64/kernel/idreg-override.c > > +++ b/arch/arm64/kernel/idreg-override.c > > @@ -262,9 +262,8 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) > > if (!len) > > return; > > > > - len = strscpy(buf, cmdline, ARRAY_SIZE(buf)); > > - if (len == -E2BIG) > > - len = ARRAY_SIZE(buf) - 1; > > + len = min(len, ARRAY_SIZE(buf) - 1); > > + strscpy(buf, cmdline, len); > > > > if (strcmp(buf, "--") == 0) > > return; > > > > > > -- > > > > Tested-by: Mostafa Saleh Cheers Mostafa. You could also just pick it, and repost it as a v2 (I really don't mind). It should give Will and Catalin a choice of implementations (and an opportunity for some additional bike-shedding ;-)). Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel