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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id k27-20020aa7973b000000b0057610894c71sm2460656pfg.209.2022.12.01.20.46.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Dec 2022 20:46:48 -0800 (PST) Date: Thu, 1 Dec 2022 20:46:47 -0800 From: Kees Cook To: Christophe JAILLET Cc: Daniel Palmer , kernel test robot , Romain Perier , Alessandro Zummo , Alexandre Belloni , "Gustavo A. R. Silva" , linux-arm-kernel@lists.infradead.org, linux-rtc@vger.kernel.org, Nathan Chancellor , Nick Desaulniers , Tom Rix , linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-hardening@vger.kernel.org Subject: Re: [PATCH] rtc: msc313: Fix function prototype mismatch in msc313_rtc_probe() Message-ID: <202212012043.C4ED0824@keescook> References: <20221118233101.never.215-kees@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221201_204653_311925_743B6DEE X-CRM114-Status: GOOD ( 34.28 ) 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="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, Nov 19, 2022 at 09:05:28AM +0100, Christophe JAILLET wrote: > Le 19/11/2022 =E0 00:31, Kees Cook a =E9crit=A0: > > With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), > > indirect call targets are validated against the expected function > > pointer prototype to make sure the call target is valid to help mitigate > > ROP attacks. If they are not identical, there is a failure at run time, > > which manifests as either a kernel panic or thread getting killed. > > = > > msc313_rtc_probe() was passing clk_disable_unprepare() directly, which > > did not have matching prototypes for devm_add_action_or_reset()'s callb= ack > > argument. Add a wrapper and remove the cast. > > = > > This was found as a result of Clang's new -Wcast-function-type-strict > > flag, which is more sensitive than the simpler -Wcast-function-type, > > which only checks for type width mismatches. > > = > > Reported-by: kernel test robot > > Link: https://lore.kernel.org/lkml/202211041527.HD8TLSE1-lkp@intel.com > > Cc: Daniel Palmer > > Cc: Romain Perier > > Cc: Alessandro Zummo > > Cc: Alexandre Belloni > > Cc: "Gustavo A. R. Silva" > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: linux-rtc@vger.kernel.org > > Signed-off-by: Kees Cook > > --- > > drivers/rtc/rtc-msc313.c | 9 ++++++++- > > 1 file changed, 8 insertions(+), 1 deletion(-) > > = > > diff --git a/drivers/rtc/rtc-msc313.c b/drivers/rtc/rtc-msc313.c > > index f3fde013c4b8..36e3e77f303e 100644 > > --- a/drivers/rtc/rtc-msc313.c > > +++ b/drivers/rtc/rtc-msc313.c > > @@ -177,6 +177,13 @@ static irqreturn_t msc313_rtc_interrupt(s32 irq, v= oid *dev_id) > > return IRQ_HANDLED; > > } > > +static void msc313_clk_disable_unprepare(void *data) > > +{ > > + struct clk *clk =3D data; > > + > > + clk_disable_unprepare(clk); > > +} > > + > > static int msc313_rtc_probe(struct platform_device *pdev) > > { > > struct device *dev =3D &pdev->dev; > > @@ -224,7 +231,7 @@ static int msc313_rtc_probe(struct platform_device = *pdev) > > return ret; > > } > > - ret =3D devm_add_action_or_reset(dev, (void (*) (void *))clk_disable_= unprepare, clk); > > + ret =3D devm_add_action_or_reset(dev, msc313_clk_disable_unprepare, c= lk); > > if (ret) > > return ret; > = > Hi, > = > another way to fix it, is to use devm_clk_get_enabled(). > = > It removes some LoC instead of introducing some new ones and saves a few > bytes of memory. Hrm, I'm not familiar with the clk stuff here -- how do I use it? Should it just be like this? (The NULL argument is ok?) diff --git a/drivers/rtc/rtc-msc313.c b/drivers/rtc/rtc-msc313.c index f3fde013c4b8..8d7737e0e2e0 100644 --- a/drivers/rtc/rtc-msc313.c +++ b/drivers/rtc/rtc-msc313.c @@ -212,22 +212,12 @@ static int msc313_rtc_probe(struct platform_device *p= dev) return ret; } = - clk =3D devm_clk_get(dev, NULL); + clk =3D devm_clk_get_enabled(dev, NULL); if (IS_ERR(clk)) { dev_err(dev, "No input reference clock\n"); return PTR_ERR(clk); } = - ret =3D clk_prepare_enable(clk); - if (ret) { - dev_err(dev, "Failed to enable the reference clock, %d\n", ret); - return ret; - } - - ret =3D devm_add_action_or_reset(dev, (void (*) (void *))clk_disable_unpr= epare, clk); - if (ret) - return ret; - rate =3D clk_get_rate(clk); writew(rate & 0xFFFF, priv->rtc_base + REG_RTC_FREQ_CW_L); writew((rate >> 16) & 0xFFFF, priv->rtc_base + REG_RTC_FREQ_CW_H); -- = Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel