From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D95F5C4345F for ; Thu, 18 Apr 2024 10:51:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=RgVaE/UdWLqFbC4Cl61WUFP2u+8q6byRmgK+0Jm7mec=; b=v+g2eXunMNjhf9 5YnP1OEOYehzPMG7HoeExiCQjHt3B2iNi9EZO4s1SyiOnha36KFsZPj9+B55UIKabCVAtS/qSK9Cy L2wFchClkXAR05BjrNG1dj0LKtDpaGX9FVI0i3tfnMfvkp5TkYB63+MD6MYYl9CxMA4qe7gnIEjpi 9CrfoVHD9LW3BEeIoGJPOalbjQSRLmL6FPPmuPjSsu6WwEF81LYfjKSZ8LS0BUidESB4GDHJD9TWk LoZZGLQk5TXJCyqul0GOHP8qXoxAaiWXMzDnmv4sqRK0qXO6uJ+EHtsU6VNZ8m39TKh28kiRLoKW4 BafcIedWNP/1TubDxvoQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rxPM3-00000001s5a-2ok6; Thu, 18 Apr 2024 10:50:59 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rxPM1-00000001s4M-1p4q for linux-arm-kernel@lists.infradead.org; Thu, 18 Apr 2024 10:50:58 +0000 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 89EBA339; Thu, 18 Apr 2024 03:51:24 -0700 (PDT) Received: from bogus (e103737-lin.cambridge.arm.com [10.1.197.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 128223F792; Thu, 18 Apr 2024 03:50:54 -0700 (PDT) Date: Thu, 18 Apr 2024 11:50:52 +0100 From: Sudeep Holla To: Beata Michalska Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, ionela.voinescu@arm.com, vanshikonda@os.amperecomputing.com, will@kernel.org, catalin.marinas@arm.com, vincent.guittot@linaro.org, sumitg@nvidia.com, yang@os.amperecomputing.com, lihuisong@huawei.com, viresh.kumar@linaro.org Subject: Re: [PATCH v5 2/5] arm64: amu: Rule out potential use after free Message-ID: <20240418105052.zvkomz5yeayie4ph@bogus> References: <20240417093848.1555462-1-beata.michalska@arm.com> <20240417093848.1555462-3-beata.michalska@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240417093848.1555462-3-beata.michalska@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240418_035057_544896_6D560316 X-CRM114-Status: GOOD ( 22.05 ) 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 Wed, Apr 17, 2024 at 10:38:45AM +0100, Beata Michalska wrote: > For the time being, the amu_fie_cpus cpumask is being exclusively used > by the AMU-related internals of FIE support and is guaranteed to be > valid on every access currently made. Still the mask is not being > invalidated on one of the error handling code paths, which leaves > a soft spot with potential risk of uaf for CPUMASK_OFFSTACK cases. > To make things sound, set the cpumaks pointer explicitly to NULL upon > failing to register the cpufreq notifier. > Note that, due to the quirks of CPUMASK_OFFSTACK, this change needs to > be wrapped with grim ifdefing (it would be better served by > incorporating this into free_cpumask_var ...) > Yes it doesn't look neat. > Signed-off-by: Beata Michalska > --- > arch/arm64/kernel/topology.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > index 1a2c72f3e7f8..3c814a278534 100644 > --- a/arch/arm64/kernel/topology.c > +++ b/arch/arm64/kernel/topology.c > @@ -244,8 +244,12 @@ static int __init init_amu_fie(void) > > ret = cpufreq_register_notifier(&init_amu_fie_notifier, > CPUFREQ_POLICY_NOTIFIER); > - if (ret) > + if (ret) { > free_cpumask_var(amu_fie_cpus); > +#ifdef CONFIG_CPUMASK_OFFSTACK > + amu_fie_cpus = NULL; > +#endif > + } Instead of this #ifdeffery, I was wondering if we can actually do the allocation in init_amu_fie_callback() the first time it gets called checking if amu_fie_cpus is NULL. init_amu_fie_callback() must get called only if the cpufreq_register_notifier() succeeds right ? Also I don't see anyone calling amu_fie_setup(), so where do you think the possible use after free could occur for amu_fie_cpus. Just thinking out loud to check if I missed anything. -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel