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 X-Spam-Level: X-Spam-Status: No, score=-15.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84E34C433E0 for ; Tue, 19 Jan 2021 18:54:10 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3D51920706 for ; Tue, 19 Jan 2021 18:54:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D51920706 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject: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=7eSDO47MiEtalfd8+k1pS9mJRKs0dLKPWvUuC/t9Uk0=; b=D4ofLzdIrRhzWUE08TBBzfq+8 QRdPBPZbKJr1uMJBSmmF7uVilLIHXiEB/cj+MF4Vql1r1V7UJ0lYqoatufaL36Jfk7uM74f6nRdLL 8WtFvGG6kNkrEvu8d3Z59VymIddJ/8Wa5wPGMWdOSPbHcqitf9k/kp9eyeWcvJZz59D1dw/ZPZXKJ Q2tKw3roVpQeVrE7x83h24NP4mua/obX2r9qHkfyIGZWgxsc6XM91MF+x0XCh7Nwg6wT9NDD1bMvX RrT8OnFYQZTsD6Xti6iZMAXeOxVDr4gGoXelfvScZ1CRY+TTbiS+RSXMrWzGBsuqZgHEm2ccXQXwN wRxsGvSGA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l1w6w-00081g-On; Tue, 19 Jan 2021 18:52:14 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l1w6t-00081L-Oi for linux-arm-kernel@lists.infradead.org; Tue, 19 Jan 2021 18:52:12 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8A55820776; Tue, 19 Jan 2021 18:52:09 +0000 (UTC) Date: Tue, 19 Jan 2021 18:52:07 +0000 From: Catalin Marinas To: Andrey Konovalov Subject: Re: [PATCH] kasan: Add explicit preconditions to kasan_report() Message-ID: <20210119185206.GA26948@gaia> References: <20210119172607.18400-1-vincenzo.frascino@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210119_135211_907626_82A8E680 X-CRM114-Status: GOOD ( 28.05 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: LKML , kasan-dev , Leon Romanovsky , Alexander Potapenko , Dmitry Vyukov , Andrey Ryabinin , Vincenzo Frascino , Linux ARM 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 Tue, Jan 19, 2021 at 07:27:43PM +0100, Andrey Konovalov wrote: > On Tue, Jan 19, 2021 at 6:26 PM Vincenzo Frascino > wrote: > > > > With the introduction of KASAN_HW_TAGS, kasan_report() dereferences > > the address passed as a parameter. > > > > Add a comment to make sure that the preconditions to the function are > > explicitly clarified. > > > > Note: An invalid address (e.g. NULL pointer address) passed to the > > function when, KASAN_HW_TAGS is enabled, leads to a kernel panic. > > > > Cc: Andrey Ryabinin > > Cc: Alexander Potapenko > > Cc: Dmitry Vyukov > > Cc: Leon Romanovsky > > Cc: Andrey Konovalov > > Signed-off-by: Vincenzo Frascino > > --- > > mm/kasan/report.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > > index c0fb21797550..2485b585004d 100644 > > --- a/mm/kasan/report.c > > +++ b/mm/kasan/report.c > > @@ -403,6 +403,17 @@ static void __kasan_report(unsigned long addr, size_t size, bool is_write, > > end_report(&flags); > > } > > > > +/** > > + * kasan_report - report kasan fault details > > + * @addr: valid address of the allocation where the tag fault was detected > > + * @size: size of the allocation where the tag fault was detected > > + * @is_write: the instruction that caused the fault was a read or write? > > + * @ip: pointer to the instruction that cause the fault > > + * > > + * Note: When CONFIG_KASAN_HW_TAGS is enabled kasan_report() dereferences > > + * the address to access the tags, hence it must be valid at this point in > > + * order to not cause a kernel panic. > > + */ > > It doesn't dereference the address, it just checks the tags, right? > > Ideally, kasan_report() should survive that with HW_TAGS like with the > other modes. The reason it doesn't is probably because of a blank > addr_has_metadata() definition for HW_TAGS in mm/kasan/kasan.h. I > guess we should somehow check that the memory comes from page_alloc or > kmalloc. Or otherwise make sure that it has tags. Maybe there's an arm > instruction to check whether the memory has tags? There isn't an architected way to probe whether a memory location has a VA->PA mapping. The tags are addressed by PA but you can't reach them if you get a page fault on the VA. So we either document the kasan_report() preconditions or, as you suggest, update addr_has_metadata() for the HW_TAGS case. Something like: return is_vmalloc_addr(virt) || virt_addr_valid(virt)); -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel