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[198.145.29.99]) by mx.google.com with ESMTPS id d31si6273902pld.161.2019.02.06.08.22.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Feb 2019 08:22:17 -0800 (PST) Received-SPF: pass (google.com: domain of srs0=f26y=qn=goodmis.org=rostedt@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; spf=pass (google.com: domain of srs0=f26y=qn=goodmis.org=rostedt@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom="SRS0=f26Y=QN=goodmis.org=rostedt@kernel.org" Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 295922175B; Wed, 6 Feb 2019 16:22:15 +0000 (UTC) Date: Wed, 6 Feb 2019 11:22:13 -0500 From: Steven Rostedt To: Rick Edgecombe Cc: Andy Lutomirski , Ingo Molnar , 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 Subject: Re: [PATCH 08/17] x86/ftrace: set trampoline pages as executable Message-ID: <20190206112213.2ec9dd5c@gandalf.local.home> In-Reply-To: <20190117003259.23141-9-rick.p.edgecombe@intel.com> References: <20190117003259.23141-1-rick.p.edgecombe@intel.com> <20190117003259.23141-9-rick.p.edgecombe@intel.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 16 Jan 2019 16:32:50 -0800 Rick Edgecombe wrote: > 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. > + */ Perhaps we should set the page to non writable after the page is updated? And set it to writable only when we need to update it. As for this patch: Reviewed-by: Steven Rostedt (VMware) -- Steve > + set_memory_x((unsigned long)trampoline, npages); > + > return (unsigned long)trampoline; > fail: > tramp_free(trampoline, *tramp_size);