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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 4E6F2C04EB8 for ; Fri, 30 Nov 2018 18:26:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1223020673 for ; Fri, 30 Nov 2018 18:26:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1223020673 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726340AbeLAFgU (ORCPT ); Sat, 1 Dec 2018 00:36:20 -0500 Received: from foss.arm.com ([217.140.101.70]:34354 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725817AbeLAFgT (ORCPT ); Sat, 1 Dec 2018 00:36:19 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 129F9165C; Fri, 30 Nov 2018 10:26:11 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D5DA83F575; Fri, 30 Nov 2018 10:26:10 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id B8FAC1AE0FA2; Fri, 30 Nov 2018 18:26:29 +0000 (GMT) Date: Fri, 30 Nov 2018 18:26:29 +0000 From: Will Deacon To: Ard Biesheuvel Cc: linux-kernel@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , Rick Edgecombe , Eric Dumazet , Jann Horn , Kees Cook , Jessica Yu , Arnd Bergmann , Catalin Marinas , Mark Rutland , "David S. Miller" , linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org Subject: Re: [PATCH v4 2/2] arm64/bpf: don't allocate BPF JIT programs in module memory Message-ID: <20181130182629.GA16085@arm.com> References: <20181123221804.440-1-ard.biesheuvel@linaro.org> <20181123221804.440-3-ard.biesheuvel@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181123221804.440-3-ard.biesheuvel@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 23, 2018 at 11:18:04PM +0100, Ard Biesheuvel wrote: > The arm64 module region is a 128 MB region that is kept close to > the core kernel, in order to ensure that relative branches are > always in range. So using the same region for programs that do > not have this restriction is wasteful, and preferably avoided. > > Now that the core BPF JIT code permits the alloc/free routines to > be overridden, implement them by vmalloc()/vfree() calls from a > dedicated 128 MB region set aside for BPF programs. This ensures > that BPF programs are still in branching range of each other, which > is something the JIT currently depends upon (and is not guaranteed > when using module_alloc() on KASLR kernels like we do currently). > It also ensures that placement of BPF programs does not correlate > with the placement of the core kernel or modules, making it less > likely that leaking the former will reveal the latter. > > This also solves an issue under KASAN, where shadow memory is > needlessly allocated for all BPF programs (which don't require KASAN > shadow pages since they are not KASAN instrumented) > > Signed-off-by: Ard Biesheuvel > --- > arch/arm64/include/asm/memory.h | 5 ++++- > arch/arm64/net/bpf_jit_comp.c | 13 +++++++++++++ > 2 files changed, 17 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h > index b96442960aea..ee20fc63899c 100644 > --- a/arch/arm64/include/asm/memory.h > +++ b/arch/arm64/include/asm/memory.h > @@ -62,8 +62,11 @@ > #define PAGE_OFFSET (UL(0xffffffffffffffff) - \ > (UL(1) << (VA_BITS - 1)) + 1) > #define KIMAGE_VADDR (MODULES_END) > +#define BPF_JIT_REGION_START (VA_START + KASAN_SHADOW_SIZE) > +#define BPF_JIT_REGION_SIZE (SZ_128M) > +#define BPF_JIT_REGION_END (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE) > #define MODULES_END (MODULES_VADDR + MODULES_VSIZE) > -#define MODULES_VADDR (VA_START + KASAN_SHADOW_SIZE) > +#define MODULES_VADDR (BPF_JIT_REGION_END) > #define MODULES_VSIZE (SZ_128M) > #define VMEMMAP_START (PAGE_OFFSET - VMEMMAP_SIZE) > #define PCI_IO_END (VMEMMAP_START - SZ_2M) > diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c > index a6fdaea07c63..76c2ab40c02d 100644 > --- a/arch/arm64/net/bpf_jit_comp.c > +++ b/arch/arm64/net/bpf_jit_comp.c > @@ -940,3 +940,16 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) > tmp : orig_prog); > return prog; > } > + > +void *bpf_jit_alloc_exec(unsigned long size) > +{ > + return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START, > + BPF_JIT_REGION_END, GFP_KERNEL, > + PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE, > + __builtin_return_address(0)); I guess we'll want VM_IMMEDIATE_UNMAP here if Rich gets that merged. In the meantime, I wonder if it's worth zeroing the region in bpf_jit_free_exec()? (although we'd need the size information...). Will