From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x226HVAyHD606OKPyS1gPgCSVT+xevnMn38clhyabZzWjvwSNwdj7sINtOnOwyTLlpyXoRx7g ARC-Seal: i=1; a=rsa-sha256; t=1518166408; cv=none; d=google.com; s=arc-20160816; b=Bh8CUjIvphiBTZbn3kf2Z/KGjD6fEmhYfG69lnfdyTXg8FVQ+1ecw1DzDAn7O+yOm+ u6maw0s4+4p9O5izNgZtNTGWVsZ9diY24D1uJLuRzWJdsXQBQv5l9DZkx8XDRYawTg5V tMcaVd+7qHiC9muQZh70EEYl8AcOjuZk95o5GVSxx2FuBsQBo49zPGDjMrSHrOLBpGQ4 OqBNkxhuaUy3L7jwxnMNEtNAsM5H2sGsgrcstKPcVwlNPDLOgmwoWXbdF0NUHdNK5hPc OMXwPFLDXpa19TP96flE+bnhg0wVWTyEOmVi0l8vmwDm+CKXN8QgbW0iV5liuOYBuvsx fscQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=spamdiagnosticmetadata:spamdiagnosticoutput :content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject :dkim-signature:arc-authentication-results; bh=vKmwubXqH297XArX2bQ1oGFXHb1eCn/nLSu3nljYbwQ=; b=nSIvhC/EeYBKNnJ+jxPx6cixjBE7zS6wTRI7r8GwGtjwvW5p2cxDF0sxIsw+0SeOOi t94+Bww/Kchzb/lElejVqununKSj2fzCIuRGsTgdMJ2T0cDpqvnqczfj2JZc7FQVGNZc bvqnOd+VY/JnuztE1wHUJARURsX5SfHtgp9O60JVxLioHMBQkDTmcvACn5lktv2vuPIm etcQUwxHp8Xjlqm6i2nkQCXmsYDMnDEHUZ5/Ggm+enhmpyOraXlEZhJvAKD3RboL2Abl d04aPuX94zWLdsEXqNIZLRoFVqnjMjmlM323GlH3pzePF62cJCmtXZZ5WhFth5LZK9HC Pl+Q== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=selector1 header.b=WcyYJ7Pb; spf=pass (google.com: domain of ktkhai@virtuozzo.com designates 40.107.4.132 as permitted sender) smtp.mailfrom=ktkhai@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=selector1 header.b=WcyYJ7Pb; spf=pass (google.com: domain of ktkhai@virtuozzo.com designates 40.107.4.132 as permitted sender) smtp.mailfrom=ktkhai@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=ktkhai@virtuozzo.com; Subject: Re: [PATCH RFC] x86: KASAN: Sanitize unauthorized irq stack access To: Matthew Wilcox , Josh Poimboeuf Cc: Dmitry Vyukov , Dave Hansen , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andrey Ryabinin , Alexander Potapenko , Andy Lutomirski , Borislav Petkov , Juergen Gross , "Kirill A. Shutemov" , Kees Cook , Mathias Krause , Greg Kroah-Hartman , Kate Stewart , LKML , kasan-dev , Linux-MM References: <151802005995.4570.824586713429099710.stgit@localhost.localdomain> <6638b09b-30b0-861e-9c00-c294889a3791@linux.intel.com> <20180208163041.zy7dbz4tlbit4i2h@treble> <20180208172026.6kqimndwyekyzzvl@treble> <20180208190016.GC9524@bombadil.infradead.org> From: Kirill Tkhai Message-ID: Date: Fri, 9 Feb 2018 11:53:19 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180208190016.GC9524@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [195.214.232.6] X-ClientProxiedBy: HE1PR05CA0188.eurprd05.prod.outlook.com (2603:10a6:3:f9::12) To HE1PR0801MB1338.eurprd08.prod.outlook.com (2603:10a6:3:39::28) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 56a51c25-7676-4abc-af26-08d56f9a935e X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(7168020)(4627221)(201703031133081)(201702281549075)(5600026)(4604075)(2017052603307)(7153060)(7193020);SRVR:HE1PR0801MB1338; 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It talks about "crappy drivers irq >> handlers when they access wrong memory on the stack". But if I >> understand correctly, the patch doesn't actually protect against that >> case, because irq handlers run on the irq stack, and this patch only >> affects code which *isn't* running on the irq stack. > > This would catch a crappy driver which allocates some memory on the > irq stack, squirrels the pointer to it away in a data structure, then > returns to process (or softirq) context and dereferences the pointer. Yes, this is exactly what I mean. The patch allows stack modifications for interrupt time, and catches wrong accesses from another contexts/cpus (when there is no interrupt executing in parallel). It's possible to catch wrong accesses in interrupt time also, but we need to unmap irq stacks on another cpus to do that, which is not KASAN thing. But, I hope we may be lucky and catch such situations even if we only check for accesses, which are going not in interrupt time. > I have no idea if that's the case that Kirill is tracking down, but it's > something I can imagine someone doing. Kirill