From patchwork Fri Apr 26 00:11:30 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nadav Amit X-Patchwork-Id: 10918621 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 871721575 for ; Fri, 26 Apr 2019 07:32:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 776C128DA2 for ; Fri, 26 Apr 2019 07:32:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6AE8628DA4; Fri, 26 Apr 2019 07:32:58 +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=-5.4 required=2.0 tests=BAYES_00,DATE_IN_PAST_06_12, RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1D76428DA3 for ; Fri, 26 Apr 2019 07:32:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726343AbfDZHcB (ORCPT ); Fri, 26 Apr 2019 03:32:01 -0400 Received: from ex13-edg-ou-002.vmware.com ([208.91.0.190]:29121 "EHLO EX13-EDG-OU-002.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726326AbfDZHcA (ORCPT ); Fri, 26 Apr 2019 03:32:00 -0400 Received: from sc9-mailhost3.vmware.com (10.113.161.73) by EX13-EDG-OU-002.vmware.com (10.113.208.156) with Microsoft SMTP Server id 15.0.1156.6; Fri, 26 Apr 2019 00:31:44 -0700 Received: from sc2-haas01-esx0118.eng.vmware.com (sc2-haas01-esx0118.eng.vmware.com [10.172.44.118]) by sc9-mailhost3.vmware.com (Postfix) with ESMTP id B36F4412A2; Fri, 26 Apr 2019 00:31:45 -0700 (PDT) From: Nadav Amit To: Peter Zijlstra , Borislav Petkov , Andy Lutomirski , Ingo Molnar CC: , , , Thomas Gleixner , Nadav Amit , Dave Hansen , , , , , , , , , , , Rick Edgecombe , Nadav Amit Subject: [PATCH v5 10/23] x86/kprobes: Set instruction page as executable Date: Thu, 25 Apr 2019 17:11:30 -0700 Message-ID: <20190426001143.4983-11-namit@vmware.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190426001143.4983-1-namit@vmware.com> References: <20190426001143.4983-1-namit@vmware.com> MIME-Version: 1.0 Received-SPF: None (EX13-EDG-OU-002.vmware.com: namit@vmware.com does not designate permitted sender hosts) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Set the page as executable after allocation. This patch is a preparatory patch for a following patch that makes module allocated pages non-executable. While at it, do some small cleanup of what appears to be unnecessary masking. Acked-by: Masami Hiramatsu Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe --- arch/x86/kernel/kprobes/core.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index a034cb808e7e..1591852d3ac4 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -431,8 +431,20 @@ void *alloc_insn_page(void) void *page; page = module_alloc(PAGE_SIZE); - if (page) - set_memory_ro((unsigned long)page & PAGE_MASK, 1); + if (!page) + return NULL; + + /* + * First make the page read-only, and only then make it executable to + * prevent it from being W+X in between. + */ + set_memory_ro((unsigned long)page, 1); + + /* + * TODO: Once additional kernel code protection mechanisms are set, ensure + * that the page was not maliciously altered and it is still zeroed. + */ + set_memory_x((unsigned long)page, 1); return page; } @@ -440,8 +452,12 @@ void *alloc_insn_page(void) /* Recover page to RW mode before releasing it */ void free_insn_page(void *page) { - set_memory_nx((unsigned long)page & PAGE_MASK, 1); - set_memory_rw((unsigned long)page & PAGE_MASK, 1); + /* + * First make the page non-executable, and only then make it writable to + * prevent it from being W+X in between. + */ + set_memory_nx((unsigned long)page, 1); + set_memory_rw((unsigned long)page, 1); module_memfree(page); }