From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B5742E0B64 for ; Thu, 10 Jul 2025 11:13:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752146025; cv=none; b=cK4zSKKNRMRtFIreL1VdRh4AOSElpskk9SkZzm1Gx3VLaLiYNUJxbRzVamZ2wkTAdirz36biBwELJ8PqPLOhkNkZ2gW8yFyGys551LwDtgaSkOh2vcdG03BbfM+pcRI0o7mxsgONTZ2V8xk8pgELXTgtpnUn0KtIA/CxFNdT488= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752146025; c=relaxed/simple; bh=OeFkcmTzr6XW9fT0eRVkKb8LuPnrMZJq6KXYNQCGwRg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Tuw3ECRsfmyAw91jZENuIexqgpulBxU9fKGp/sTASGYLuMbfUOje0g2zBa7uAptJqnqI5F8XhoUs8eAbRfMb5eXptIe3KOXtgem88k6ujRcnHgl5nu8ERjGYz/xJvKRKt3Q5NIxSRXhpUyxpZ+N8q8pQjQaIWhzgmv8S5/5zwSk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=bNYc+4F9; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="bNYc+4F9" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=QSYKDb138GvI+dxArsFvp9SqY4NfAKhkZ1mgvvFaOHQ=; b=bNYc+4F9oiti9nQQ0HdkVnoDdm zO5nQjNhq+oRe52+ZVhWMirI91miX0SMt0Gq36WOAXpTs7+F5BMVPE4EqYsSYvAPANO+5+CwV2PxS ZQcH8snzQEMoYokm9YcFaaMzdIAmw2P+u7OBF6GU0m6B0WFM6V48Xxf4J+6MRr/oB77NsvciN9Zt+ suUbxn5N9JFWBU1x8gGYGxQ433NMS1AJ7Ms1+E58+E2NJTHvxW0uP8Zz0eQIPNz24ftHx4nVFvhlB Dr2LD8ubTYCq71PrvBgFbcQV3TMCeUuhUApHdPh4g0ER72SOQVnbNuhQB9o4641mFwfppfJuXRDRQ fGQlfElA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1uZpDa-000000090A1-3zIF; Thu, 10 Jul 2025 11:13:35 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 7FB4C300125; Thu, 10 Jul 2025 13:13:34 +0200 (CEST) Date: Thu, 10 Jul 2025 13:13:34 +0200 From: Peter Zijlstra To: Zicheng Qu Cc: mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, tanghui20@huawei.com, zhangqiao22@huawei.com, judy.chenhui@huawei.com Subject: Re: [PATCH] sched/fair: Fix overflow in vruntime_eligible() causing NULL return Message-ID: <20250710111334.GD542000@noisy.programming.kicks-ass.net> References: <20250709093829.3213647-1-quzicheng@huawei.com> <20250709115317.GK1613200@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Jul 10, 2025 at 10:01:15AM +0800, Zicheng Qu wrote: > Hi, > > Based on LTS 6.6. I also looked at the code logic around vruntime_eligible() > in the mainline. It seems that if vruntime_eligible() consistently returned > false, this could lead to null pointer dereferences. That is a truly ancient kernel. Please verify the issue is reproducible on something recent. Specifically, commit bbce3de72be5 ("sched/eevdf: Fix se->slice being set to U64_MAX and resulting crash") cured something very similar to this.