From patchwork Wed Apr 3 17:34:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Khalid Aziz X-Patchwork-Id: 10884289 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 18A4717E1 for ; Wed, 3 Apr 2019 17:37:13 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F26B727FA8 for ; Wed, 3 Apr 2019 17:37:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E49C4288F4; Wed, 3 Apr 2019 17:37:12 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 3615227FA8 for ; Wed, 3 Apr 2019 17:37:10 +0000 (UTC) Received: (qmail 30409 invoked by uid 550); 3 Apr 2019 17:37:09 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 30391 invoked from network); 3 Apr 2019 17:37:08 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : in-reply-to : references; s=corp-2018-07-02; bh=RQ6cfPE1oUdZhXOBb8lEKxLwdCK2MCPnapeo9zEXamM=; b=FCi26eH2yuIj/duNDQmSbddnHqKIgNwk5FitB/zF8l+pOrUfoRX+prFRbpqHu9Gr/3ss /IeG8UwqR1hfVmbLtEDQOcWMydXrIwj2ToNVug5qC2TokZppKngyobnDY6VBcytWlju/ oghOni+CK13eoXN4LvOyT8p5rYzAopR3y2MzmG0ZokbUJRieoruWDXzmgm834RPzDZ0Z V6YURMu87c3OumnQbKDenDg00eEPn5Z2IV7lnjC3ZZb4z+7P5Ga4/1YizcEZKAsQL2Jq rlwWi8L/5Lw5w+WDr7wK1Pjj1zc6Lhid+jNfzqvpM10qAhdsz56CtubdeBhgq1tKGrJM Zg== From: Khalid Aziz To: juergh@gmail.com, tycho@tycho.ws, jsteckli@amazon.de, ak@linux.intel.com, liran.alon@oracle.com, keescook@google.com, konrad.wilk@oracle.com Cc: deepa.srinivasan@oracle.com, chris.hyser@oracle.com, tyhicks@canonical.com, dwmw@amazon.co.uk, andrew.cooper3@citrix.com, jcm@redhat.com, boris.ostrovsky@oracle.com, kanth.ghatraju@oracle.com, joao.m.martins@oracle.com, jmattson@google.com, pradeep.vincent@oracle.com, john.haxby@oracle.com, tglx@linutronix.de, kirill.shutemov@linux.intel.com, hch@lst.de, steven.sistare@oracle.com, labbott@redhat.com, luto@kernel.org, dave.hansen@intel.com, peterz@infradead.org, aaron.lu@intel.com, akpm@linux-foundation.org, alexander.h.duyck@linux.intel.com, amir73il@gmail.com, andreyknvl@google.com, aneesh.kumar@linux.ibm.com, anthony.yznaga@oracle.com, ard.biesheuvel@linaro.org, arnd@arndb.de, arunks@codeaurora.org, ben@decadent.org.uk, bigeasy@linutronix.de, bp@alien8.de, brgl@bgdev.pl, catalin.marinas@arm.com, corbet@lwn.net, cpandya@codeaurora.org, daniel.vetter@ffwll.ch, dan.j.williams@intel.com, gregkh@linuxfoundation.org, guro@fb.com, hannes@cmpxchg.org, hpa@zytor.com, iamjoonsoo.kim@lge.com, james.morse@arm.com, jannh@google.com, jgross@suse.com, jkosina@suse.cz, jmorris@namei.org, joe@perches.com, jrdr.linux@gmail.com, jroedel@suse.de, keith.busch@intel.com, khalid.aziz@oracle.com, khlebnikov@yandex-team.ru, logang@deltatee.com, marco.antonio.780@gmail.com, mark.rutland@arm.com, mgorman@techsingularity.net, mhocko@suse.com, mhocko@suse.cz, mike.kravetz@oracle.com, mingo@redhat.com, mst@redhat.com, m.szyprowski@samsung.com, npiggin@gmail.com, osalvador@suse.de, paulmck@linux.vnet.ibm.com, pavel.tatashin@microsoft.com, rdunlap@infradead.org, richard.weiyang@gmail.com, riel@surriel.com, rientjes@google.com, robin.murphy@arm.com, rostedt@goodmis.org, rppt@linux.vnet.ibm.com, sai.praneeth.prakhya@intel.com, serge@hallyn.com, steve.capper@arm.com, thymovanbeers@gmail.com, vbabka@suse.cz, will.deacon@arm.com, willy@infradead.org, yang.shi@linux.alibaba.com, yaojun8558363@gmail.com, ying.huang@intel.com, zhangshaokun@hisilicon.com, iommu@lists.linux-foundation.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, Khalid Aziz , kernel-hardening@lists.openwall.com, "Vasileios P . Kemerlis" , Juerg Haefliger , David Woodhouse Subject: [RFC PATCH v9 11/13] xpfo, mm: optimize spinlock usage in xpfo_kunmap Date: Wed, 3 Apr 2019 11:34:12 -0600 Message-Id: <5bab13e12d4215112ad2180106cc6bb9b513754a.1554248002.git.khalid.aziz@oracle.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: References: In-Reply-To: References: X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9216 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904030118 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9216 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=952 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904030118 X-Virus-Scanned: ClamAV using ClamSMTP From: Julian Stecklina Only the xpfo_kunmap call that needs to actually unmap the page needs to be serialized. We need to be careful to handle the case, where after the atomic decrement of the mapcount, a xpfo_kmap increased the mapcount again. In this case, we can safely skip modifying the page table. Model-checked with up to 4 concurrent callers with Spin. Signed-off-by: Julian Stecklina Signed-off-by: Khalid Aziz Cc: Khalid Aziz Cc: x86@kernel.org Cc: kernel-hardening@lists.openwall.com Cc: Vasileios P. Kemerlis Cc: Juerg Haefliger Cc: Tycho Andersen Cc: Marco Benatto Cc: David Woodhouse --- include/linux/xpfo.h | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) diff --git a/include/linux/xpfo.h b/include/linux/xpfo.h index 2318c7eb5fb7..37e7f52fa6ce 100644 --- a/include/linux/xpfo.h +++ b/include/linux/xpfo.h @@ -61,6 +61,7 @@ static inline void xpfo_kmap(void *kaddr, struct page *page) static inline void xpfo_kunmap(void *kaddr, struct page *page) { unsigned long flags; + bool flush_tlb = false; if (!static_branch_unlikely(&xpfo_inited)) return; @@ -72,18 +73,23 @@ static inline void xpfo_kunmap(void *kaddr, struct page *page) * The page is to be allocated back to user space, so unmap it from * the kernel, flush the TLB and tag it as a user page. */ - spin_lock_irqsave(&page->xpfo_lock, flags); - if (atomic_dec_return(&page->xpfo_mapcount) == 0) { -#ifdef CONFIG_XPFO_DEBUG - WARN_ON(PageXpfoUnmapped(page)); -#endif - SetPageXpfoUnmapped(page); - set_kpte(kaddr, page, __pgprot(0)); - xpfo_flush_kernel_tlb(page, 0); + spin_lock_irqsave(&page->xpfo_lock, flags); + + /* + * In the case, where we raced with kmap after the + * atomic_dec_return, we must not nuke the mapping. + */ + if (atomic_read(&page->xpfo_mapcount) == 0) { + SetPageXpfoUnmapped(page); + set_kpte(kaddr, page, __pgprot(0)); + flush_tlb = true; + } + spin_unlock_irqrestore(&page->xpfo_lock, flags); } - spin_unlock_irqrestore(&page->xpfo_lock, flags); + if (flush_tlb) + xpfo_flush_kernel_tlb(page, 0); } void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp, bool will_map);