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 190D1C433EF for ; Tue, 25 Jan 2022 16:11:01 +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=arjIwHnOcU8sx6gYNIyAgiTbx7KpVV1V7IBCCo64gik=; b=HC1/rt3fJ1TV1k 1HPOCVwoy6mzcmZp8WonQCvxgw8NeqZ5ddEmQjxmfa1nv40FgdAToaI2P93Wtv6s9SjRHJGgibQXy vOv5poSm+lmrN6edWGyyLZU9CBUGOAdTOUWUF2StV0s5g1s3kl3Ydf+aiCa0nNH1oBCetsN1rPw6M ipxUFO2Dh/YUfZDKsWL2EyhohcZW4ehlkEYYuRybL0dgPeMe8jDfO3NqobJAXcCDNtQI7fegXSqWS TiDawklh9XVbmMMmbuGvD1It0vEm4DnuI/QBj1oBdlLyEoUs9kuysXl6cp7xZBPKeBwRUKJdsagbv 4pO4N1/QRPwpOZxlsV5w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nCONu-008Zre-62; Tue, 25 Jan 2022 16:09:30 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nCO5A-008TAH-P4 for linux-arm-kernel@lists.infradead.org; Tue, 25 Jan 2022 15:50:10 +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 2F1C9D6E; Tue, 25 Jan 2022 07:50:08 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.1.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BCC023F793; Tue, 25 Jan 2022 07:50:06 -0800 (PST) Date: Tue, 25 Jan 2022 15:50:01 +0000 From: Mark Rutland To: Evgenii Stepanov Cc: Catalin Marinas , Will Deacon , Ard Biesheuvel , Robin Murphy , Jisheng Zhang , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: extable: fix null deref in load_unaligned_zeropad. Message-ID: References: <20220122023447.1480995-1-eugenis@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220125_075008_911367_9761C60D X-CRM114-Status: GOOD ( 17.67 ) 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 Tue, Jan 25, 2022 at 03:23:20PM +0000, Mark Rutland wrote: > On Fri, Jan 21, 2022 at 06:34:47PM -0800, Evgenii Stepanov wrote: > > ex_handler_load_unaligned_zeropad extracts the source and data register > > numbers from the wrong field of the exception table. > > Ouch. Did you find this by inspection, or did this show up in testing? > > Sorry about this. > > I think we should be a little more explicit as to exactly what goes wrong. How > about: > > | In ex_handler_load_unaligned_zeropad() we erroneously extract the data and > | addr register indices from ex->type rather than ex->data. As ex->type will > | contain EX_TYPE_LOAD_UNALIGNED_ZEROPAD (i.e. 4): > | > | * We'll always treat X0 as the address register, since EX_DATA_REG_ADDR is > | extracted from bits [9:5]. Thus, we may attempt to dereference an arbitrary > | address as X0 may hold an arbitary value. > | > | * We'll always treat X4 as the data register, since EX_DATA_REG_DATA is > | extracted from bits [4:0]. Thus we will corrupt X4 and cause arbitrary > | behaviour within load_unaligned_zeropad() and its caller. > | > | Fix this by extracting both values from ex->data as originally intended. > > > Fixes: 753b3236 > > That should be expanded, e.g. > > Fixes: 753b32368705c396 ("arm64: extable: add load_unaligned_zeropad() handler") > > With those changes: > > Reviewed-by: Mark Rutland Looking again, sicne this isn't jsut a null-deref, can we also rework the title, something like: | arm64: extable: fix load_unaligned_zeropad() reg indices Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel