From patchwork Thu May 30 03:03:57 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 10968109 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 3B2F2912 for ; Thu, 30 May 2019 03:17:03 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 276A428A41 for ; Thu, 30 May 2019 03:17:03 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1660E28A4C; Thu, 30 May 2019 03:17:03 +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=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 C465A28A41 for ; Thu, 30 May 2019 03:17:01 +0000 (UTC) Received: (qmail 1745 invoked by uid 550); 30 May 2019 03:17:00 -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 1701 invoked from network); 30 May 2019 03:16:59 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559186207; bh=n+mQP6Ot/bSNwz8Z1NLu1w72gjU1a7QBXhVgmvvJSEs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=atqCpRwY9Yc7Gg4jFZ0ruHrpfDw5TrJVNIIxX3mvPome4YrCwW6Z1BCsMm0ltYUrd pLyT3UUTAtP0WcdKd20qo92HXe96LC+c0vRa+lZ0nJbx9J6h3lOzmdpIc34XKLNZwg wJiyXesycslhSFDM9Jp8ybVSfP5vrQegcHudJVpE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , Andy Lutomirski , Nadav Amit , Rick Edgecombe , "Peter Zijlstra (Intel)" , akpm@linux-foundation.org, ard.biesheuvel@linaro.org, deneen.t.dock@intel.com, kernel-hardening@lists.openwall.com, kristen@linux.intel.com, linux_dti@icloud.com, will.deacon@arm.com, Andy Lutomirski , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Jessica Yu , Kees Cook , Linus Torvalds , Masami Hiramatsu , Rik van Riel , Ingo Molnar , Sasha Levin Subject: [PATCH 4.19 079/276] x86/modules: Avoid breaking W^X while loading modules Date: Wed, 29 May 2019 20:03:57 -0700 Message-Id: <20190530030531.331779845@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190530030523.133519668@linuxfoundation.org> References: <20190530030523.133519668@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP [ Upstream commit f2c65fb3221adc6b73b0549fc7ba892022db9797 ] When modules and BPF filters are loaded, there is a time window in which some memory is both writable and executable. An attacker that has already found another vulnerability (e.g., a dangling pointer) might be able to exploit this behavior to overwrite kernel code. Prevent having writable executable PTEs in this stage. In addition, avoiding having W+X mappings can also slightly simplify the patching of modules code on initialization (e.g., by alternatives and static-key), as would be done in the next patch. This was actually the main motivation for this patch. To avoid having W+X mappings, set them initially as RW (NX) and after they are set as RO set them as X as well. Setting them as executable is done as a separate step to avoid one core in which the old PTE is cached (hence writable), and another which sees the updated PTE (executable), which would break the W^X protection. Suggested-by: Thomas Gleixner Suggested-by: Andy Lutomirski Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Cc: Cc: Cc: Cc: Cc: Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: H. Peter Anvin Cc: Jessica Yu Cc: Kees Cook Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Rik van Riel Link: https://lkml.kernel.org/r/20190426001143.4983-12-namit@vmware.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- arch/x86/kernel/alternative.c | 28 +++++++++++++++++++++------- arch/x86/kernel/module.c | 2 +- include/linux/filter.h | 1 + kernel/module.c | 5 +++++ 4 files changed, 28 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index b9d5e7c9ef43e..918a23704c0c5 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -662,15 +662,29 @@ void __init alternative_instructions(void) * handlers seeing an inconsistent instruction while you patch. */ void *__init_or_module text_poke_early(void *addr, const void *opcode, - size_t len) + size_t len) { unsigned long flags; - local_irq_save(flags); - memcpy(addr, opcode, len); - local_irq_restore(flags); - sync_core(); - /* Could also do a CLFLUSH here to speed up CPU recovery; but - that causes hangs on some VIA CPUs. */ + + if (boot_cpu_has(X86_FEATURE_NX) && + is_module_text_address((unsigned long)addr)) { + /* + * Modules text is marked initially as non-executable, so the + * code cannot be running and speculative code-fetches are + * prevented. Just change the code. + */ + memcpy(addr, opcode, len); + } else { + local_irq_save(flags); + memcpy(addr, opcode, len); + local_irq_restore(flags); + sync_core(); + + /* + * Could also do a CLFLUSH here to speed up CPU recovery; but + * that causes hangs on some VIA CPUs. + */ + } return addr; } diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c index f58336af095c9..6645f123419c6 100644 --- a/arch/x86/kernel/module.c +++ b/arch/x86/kernel/module.c @@ -87,7 +87,7 @@ void *module_alloc(unsigned long size) p = __vmalloc_node_range(size, MODULE_ALIGN, MODULES_VADDR + get_module_load_offset(), MODULES_END, GFP_KERNEL, - PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE, + PAGE_KERNEL, 0, NUMA_NO_NODE, __builtin_return_address(0)); if (p && (kasan_module_alloc(p, size) < 0)) { vfree(p); diff --git a/include/linux/filter.h b/include/linux/filter.h index 6ecef32fd8bcd..d52a7484aeb2d 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -684,6 +684,7 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp) static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr) { set_memory_ro((unsigned long)hdr, hdr->pages); + set_memory_x((unsigned long)hdr, hdr->pages); } static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr) diff --git a/kernel/module.c b/kernel/module.c index 38bf28b5cc202..f797c6ace7121 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1949,8 +1949,13 @@ void module_enable_ro(const struct module *mod, bool after_init) return; frob_text(&mod->core_layout, set_memory_ro); + frob_text(&mod->core_layout, set_memory_x); + frob_rodata(&mod->core_layout, set_memory_ro); + frob_text(&mod->init_layout, set_memory_ro); + frob_text(&mod->init_layout, set_memory_x); + frob_rodata(&mod->init_layout, set_memory_ro); if (after_init)