From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3CEB9219ED for ; Fri, 16 Feb 2024 17:21:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708104069; cv=none; b=LRyZZKQHkuOuDaDyncujC2Kgx60wV3p3PxKz4iw5h2VPfP2ZyugCyjCVrOLxaCxaKnJ0/n0BXn74/6t+PT7FCFp4C3w8dSZ/FczCwMhQYjgrnLF3KlWebN4UTkAems1bCdRjZ3qwRYH2mopHNL7PwLya07Lvh3figpmrRHciXpc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708104069; c=relaxed/simple; bh=yESAlwHUyoqJ9dwcB3Qp++fB/3R3GtWL28LNJ36pRc8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HrHX3Ub2BD6fZ+tZ6kj36lrCqOShAQzUdOQ8L5nG9Wa+hDwX9S82313vS8buvzjqefxTwYThBuY4z1HP3n6jVs3SH67B3KJu/5yrL4IvTdXhTq5JOscH44aMzFJ5662RRGgbtAAVrbw8u2SAkuMCV0kdrd+kTegN2q8nH/DYSM0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 29067DA7; Fri, 16 Feb 2024 09:21:47 -0800 (PST) Received: from pluto (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A04A63F694; Fri, 16 Feb 2024 09:21:04 -0800 (PST) Date: Fri, 16 Feb 2024 17:21:02 +0000 From: Cristian Marussi To: Arnd Bergmann Cc: Sudeep Holla , Arnd Bergmann , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH] firmware: arm_scmi: avoid returning uninialized data Message-ID: References: <20240216163259.1927967-1-arnd@kernel.org> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240216163259.1927967-1-arnd@kernel.org> On Fri, Feb 16, 2024 at 05:32:53PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann > > Clang notices that there is a code path through > scmi_powercap_notify_supported() that returns an > undefined value: > Hi Arnd, > drivers/firmware/arm_scmi/powercap.c:821:11: error: variable 'supported' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized] > 821 | else if (evt_id == SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > drivers/firmware/arm_scmi/powercap.c:824:9: note: uninitialized use occurs here > 824 | return supported; > | ^~~~~~~~~ > drivers/firmware/arm_scmi/powercap.c:821:7: note: remove the 'if' if its condition is always true > 821 | else if (evt_id == SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 822 | supported = dom_info->notify_powercap_measurement_change; > drivers/firmware/arm_scmi/powercap.c:811:16: note: initialize the variable 'supported' to silence this warning > 811 | bool supported; > | ^ > > Return 'false' here, which is probably what was intended. > > Fixes: c92a75fe84ce ("firmware: arm_scmi: Implement Powercap .is_notify_supported callback") > Signed-off-by: Arnd Bergmann thanks for looking at this, this series that I've just posted is still to be reviewd at all, so I would expect issues :D...BUT in this case I dont think that the clang report is valid since, inside the culprit function scmi_powercap_notify_supported(), a few lines before the reported usage of unitialized data there is a check (@line 816) on the 'bounds' of evt_id itself if (evt_id >= ARRAY_SIZE(evt_2_cmd) || src_id >= pi->num_domains) return false; so basically the mentioned if/else WILL be evaluated in some of its branches for sure and supported wont be uninitialized. Indeed, I removed from here (and from all the series) the explicit initialization at definition time right before posting the series. Having saidm that...maybe it is just brain-dead this approach of mine since it is able to fool clang & friends...I would add bACK an explicit initialization of supported all across this series in V2, if this sounds good to you. Thanks, Cristian > --- > drivers/firmware/arm_scmi/powercap.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/firmware/arm_scmi/powercap.c b/drivers/firmware/arm_scmi/powercap.c > index aae91f47303e..8ee3be8776b0 100644 > --- a/drivers/firmware/arm_scmi/powercap.c > +++ b/drivers/firmware/arm_scmi/powercap.c > @@ -820,6 +820,8 @@ scmi_powercap_notify_supported(const struct scmi_protocol_handle *ph, > supported = dom_info->notify_powercap_cap_change; > else if (evt_id == SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED) > supported = dom_info->notify_powercap_measurement_change; > + else > + supported = false; > > return supported; > } > -- > 2.39.2 >