From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id 649098E0002 for ; Wed, 16 Jan 2019 19:35:05 -0500 (EST) Received: by mail-pg1-f198.google.com with SMTP id r16so5013956pgr.15 for ; Wed, 16 Jan 2019 16:35:05 -0800 (PST) Received: from mga04.intel.com (mga04.intel.com. [192.55.52.120]) by mx.google.com with ESMTPS id 1si7848435plo.195.2019.01.16.16.33.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 16 Jan 2019 16:33:39 -0800 (PST) From: Rick Edgecombe Subject: [PATCH 08/17] x86/ftrace: set trampoline pages as executable Date: Wed, 16 Jan 2019 16:32:50 -0800 Message-Id: <20190117003259.23141-9-rick.p.edgecombe@intel.com> In-Reply-To: <20190117003259.23141-1-rick.p.edgecombe@intel.com> References: <20190117003259.23141-1-rick.p.edgecombe@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andy Lutomirski , Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, Thomas Gleixner , Borislav Petkov , Nadav Amit , Dave Hansen , Peter Zijlstra , linux_dti@icloud.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, akpm@linux-foundation.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, will.deacon@arm.com, ard.biesheuvel@linaro.org, kristen@linux.intel.com, deneen.t.dock@intel.com, Nadav Amit , Steven Rostedt , Rick Edgecombe From: Nadav Amit Since alloc_module() will not set the pages as executable soon, we need to do so for ftrace trampoline pages after they are allocated. For the time being, we do not change ftrace to use the text_poke() interface. As a result, ftrace breaks still breaks W^X. Cc: Steven Rostedt Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe --- arch/x86/kernel/ftrace.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 8257a59704ae..eb4a1937e72c 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -742,6 +742,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) unsigned long end_offset; unsigned long op_offset; unsigned long offset; + unsigned long npages; unsigned long size; unsigned long retq; unsigned long *ptr; @@ -774,6 +775,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) return 0; *tramp_size = size + RET_SIZE + sizeof(void *); + npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE); /* Copy ftrace_caller onto the trampoline memory */ ret = probe_kernel_read(trampoline, (void *)start_offset, size); @@ -818,6 +820,13 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) /* ALLOC_TRAMP flags lets us know we created it */ ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP; + /* + * Module allocation needs to be completed by making the page + * executable. The page is still writable, which is a security hazard, + * but anyhow ftrace breaks W^X completely. + */ + set_memory_x((unsigned long)trampoline, npages); + return (unsigned long)trampoline; fail: tramp_free(trampoline, *tramp_size); -- 2.17.1