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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 406ADC433E0 for ; Wed, 27 May 2020 21:19:53 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 0812B207E8 for ; Wed, 27 May 2020 21:19:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="LQMU1vFp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0812B207E8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=EwRVFUAUKxlKst1cgd0PVNK+ybKZqgG8LT/PSgxiSOs=; b=LQMU1vFpInfF1YPfdD3MgisgWi DFIHDrGAD+jMI6bE/vPDNS/xnqhUkrrEEOWoK6yLyNhvLKuT7syln5zDSekMMGWPt57u1wzdGw9DE Q/dX1uInAlyQiFr/CSgT3yo1Jdeyz0ZM17BeDZvTpaADnWi8nCxsgtp9IdbWSXTvG9Nbtj1ZaSJlE JXH3gsJPxgg0flc6l+9x5aflb+A5/HuH2OJ0XGNABjVqELEkVgF2qxva17s5woM61JKHJmhu81Et7 QcniHqfIJLlSJ3+n2nJdM0nu45nk2fKpbM6aYMwXCif7Ac0/UB7Gl4H6rUznm5fg7FL6iOF6XUBdp fXQZlNMQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1je3Sh-0002M6-1d; Wed, 27 May 2020 21:19:43 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1je3RY-0001O8-CP for linux-arm-kernel@lists.infradead.org; Wed, 27 May 2020 21:18:36 +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 1D3CB1045; Wed, 27 May 2020 14:18:31 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 022963F52E; Wed, 27 May 2020 14:18:29 -0700 (PDT) From: Dave Martin To: Michael Kerrisk Subject: [PATCH v2 5/6] prctl.2: Add PR_PAC_RESET_KEYS (arm64) Date: Wed, 27 May 2020 22:17:37 +0100 Message-Id: <1590614258-24728-6-git-send-email-Dave.Martin@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1590614258-24728-1-git-send-email-Dave.Martin@arm.com> References: <1590614258-24728-1-git-send-email-Dave.Martin@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200527_141832_521888_2E8C8D0D X-CRM114-Status: GOOD ( 11.42 ) 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: linux-arch@vger.kernel.org, linux-man@vger.kernel.org, Catalin Marinas , Amit Daniel Kachhap , Mark Rutland , Will Deacon , linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Add documentation for the PR_PAC_RESET_KEYS ioctl added in Linux 5.0 for arm64. Signed-off-by: Dave Martin Cc: Will Deacon Cc: Catalin Marinas Cc: Amit Daniel Kachhap Cc: Mark Rutland --- Since v1: * Clarify explicitly that PR_PAC_RESET_KEYS is redundant when combined with execve(). * Move error condition details into the prctl description, to avoid excessive duplication while keeping keeping related pieces of text closer together. * In lieu of having a separate man page to cross reference for detailed guidance, cross-reference the kernel documentation. * Add safety warning. This is deliberately vague, pending ongoing discussions with libc folks. --- man2/prctl.2 | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) diff --git a/man2/prctl.2 b/man2/prctl.2 index 91df7c8..3ee2702 100644 --- a/man2/prctl.2 +++ b/man2/prctl.2 @@ -950,6 +950,77 @@ behavior. A value of 1 indicates .BR execve (2) will operate in the privilege-restricting mode described above. +.\" prctl PR_PAC_RESET_KEYS +.\" commit ba830885656414101b2f8ca88786524d4bb5e8c1 +.TP +.BR PR_PAC_RESET_KEYS " (since Linux 5.0, only on arm64)" +Securely reset the thread's pointer authentication keys +to fresh random values generated by the kernel. +.IP +The set of keys to be reset is specified by +.IR arg2 , +which must be a logical OR of zero or more of the following: +.RS +.TP +.B PR_PAC_APIAKEY +instruction authentication key A +.TP +.B PR_PAC_APIBKEY +instruction authentication key B +.TP +.B PR_PAC_APDAKEY +data authentication key A +.TP +.B PR_PAC_APDBKEY +data authentication key B +.TP +.B PR_PAC_APGAKEY +generic authentication \(lqA\(rq key. +.IP +(Yes folks, there really is no generic B key.) +.RE +.IP +As a special case, if +.I arg2 +is zero then all the keys are reset. +Since new keys could be added in future, +this is the recommended way to completely wipe the existing keys +when establishing a clean execution context. +Note that there is no need to use +.BR PR_PAC_RESET_KEYS +in preparation for calling +.BR execve (2), +since +.BR execve (2) +resets all the pointer authentication keys. +.IP +The remaining arguments +.IR arg3 ", " arg4 " and " arg5 +must all be zero. +.IP +If the arguments are invalid, +and in particular if +.I arg2 +contains set bits that are unrecognized +or that correspond to a key not available on this platform, +the call fails with error +.BR EINVAL . +.IP +.B Warning: +Because the compiler or run-time environment +may be using some or all of the keys, +a successful +.IP +For more information, see the kernel source file +.I Documentation/arm64/pointer\-authentication.rst +.\"commit b693d0b372afb39432e1c49ad7b3454855bc6bed +(or +.I Documentation/arm64/pointer\-authentication.txt +before Linux 5.3). +.B PR_PAC_RESET_KEYS +may crash the calling process. +The conditions for using it safely are complex and system-dependent. +Don't use it unless you know what you are doing. .\" prctl PR_SET_PDEATHSIG .TP .BR PR_SET_PDEATHSIG " (since Linux 2.1.57)" @@ -1964,6 +2035,15 @@ are not 0. .B EINVAL .I option is +.B PR_PAC_RESET_KEYS +and the arguments are invalid or unsupported. +See the description of +.B PR_PAC_RESET_KEYS +above for details. +.TP +.B EINVAL +.I option +is .B PR_SVE_SET_VL and the arguments are invalid or unsupported, or SVE is not available on this platform. -- 2.1.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel