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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 520D0C282C2 for ; Thu, 7 Feb 2019 16:40:07 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 9A55D2173B for ; Thu, 7 Feb 2019 16:40:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A55D2173B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 43wPDh1lTyzDqS5 for ; Fri, 8 Feb 2019 03:40:04 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=bauerman@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 43wPBm37jxzDqRn for ; Fri, 8 Feb 2019 03:38:23 +1100 (AEDT) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x17GZbig048022 for ; Thu, 7 Feb 2019 11:38:21 -0500 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0b-001b2d01.pphosted.com with ESMTP id 2qgp0b86r0-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 07 Feb 2019 11:38:18 -0500 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 7 Feb 2019 16:38:10 -0000 Received: from b01ledav006.gho.pok.ibm.com (b01ledav006.gho.pok.ibm.com [9.57.199.111]) by b01cxnp22033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x17Gc9nG14221546 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 7 Feb 2019 16:38:09 GMT Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CC961AC060; Thu, 7 Feb 2019 16:38:08 +0000 (GMT) Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 27C08AC05B; Thu, 7 Feb 2019 16:38:08 +0000 (GMT) Received: from morokweng.localdomain (unknown [9.85.156.8]) by b01ledav006.gho.pok.ibm.com (Postfix) with ESMTPS; Thu, 7 Feb 2019 16:38:07 +0000 (GMT) References: <20190206062837.26917-1-ruscur@russell.cc> <1549515373.con208q1rq.astroid@bobo.none> User-agent: mu4e 1.0; emacs 26.1 From: Thiago Jung Bauermann To: Russell Currey Subject: Re: [PATCH] powerpc/powernv/idle: Restore IAMR after idle In-reply-to: Date: Thu, 07 Feb 2019 14:37:58 -0200 MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 x-cbid: 19020716-0068-0000-0000-0000038FA3F8 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010554; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000279; SDB=6.01157671; UDB=6.00603986; IPR=6.00938202; MB=3.00025481; MTD=3.00000008; XFM=3.00000015; UTC=2019-02-07 16:38:11 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19020716-0069-0000-0000-0000476BAA2B Message-Id: <878syrlfnf.fsf@morokweng.localdomain> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-02-07_11:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=520 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902070126 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Russell Currey writes: > On Thu, 2019-02-07 at 15:08 +1000, Nicholas Piggin wrote: >> Russell Currey's on February 6, 2019 4:28 pm: >> > Without restoring the IAMR after idle, execution prevention on >> > POWER9 >> > with Radix MMU is overwritten and the kernel can freely execute >> > userspace without >> > faulting. >> > >> > This is necessary when returning from any stop state that modifies >> > user >> > state, as well as hypervisor state. >> > >> > To test how this fails without this patch, load the lkdtm driver >> > and >> > do the following: >> > >> > echo EXEC_USERSPACE > /sys/kernel/debug/provoke-crash/DIRECT >> > >> > which won't fault, then boot the kernel with powersave=off, where >> > it >> > will fault. Applying this patch will fix this. >> > >> > Fixes: 3b10d0095a1e ("powerpc/mm/radix: Prevent kernel execution of >> > user >> > space") >> > Cc: >> > Signed-off-by: Russell Currey >> >> Good catch and debugging. This really should be a quirk, we don't >> want >> to have to restore this thing on a thread switch. >> >> Can we put it under a CONFIG option if we're not using IAMR? > > I don't exactly know when we do or don't use the IAMR (since the only > thing I've used it for is radix). When wouldn't we care about > restoring it on hash? On hash it's used for memory protection keys (code is in arch/powerpc/mm/pkeys.c). The kernel doesn't use protection keys, but userspace apps may use it explicitly via specific syscalls (pkey_alloc(), pkey_mprotect, pkey_free()). Also, the kernel may use a protection key if the process does an mmap(PROT_EXEC). -- Thiago Jung Bauermann IBM Linux Technology Center