From patchwork Thu Aug 12 08:43:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12432913 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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 2EEF2C4320A for ; Thu, 12 Aug 2021 08:45:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D15A6108C for ; Thu, 12 Aug 2021 08:45:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235260AbhHLIqE (ORCPT ); Thu, 12 Aug 2021 04:46:04 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:23873 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235155AbhHLIqD (ORCPT ); Thu, 12 Aug 2021 04:46:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628757938; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oGlOCkBYoC0XEBY+vyOkFgZAXDwE68Y66i/B8dT24gA=; b=KIN1/ShBSzmf8GbkyocAX6AXw5ccEFMnmLpoI5lBpAF/PoapFeqHL1LCAm3Ix040h3APpS S+ClQ+bjUzrSqUsWC94xBBf4lucfS6rHqyh7odgGuDmI7/J8ah4j8onf+KWw1bueBoy69v Cs9mJo+x6aZs64s9ob/4jwr7DgG7dlY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-188-cEBDOImuP2GzXYhS9Fp4CQ-1; Thu, 12 Aug 2021 04:45:35 -0400 X-MC-Unique: cEBDOImuP2GzXYhS9Fp4CQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2941587D544; Thu, 12 Aug 2021 08:45:34 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.193.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id EEC1B5FC22; Thu, 12 Aug 2021 08:45:13 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Linus Torvalds , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Alexander Viro , Alexey Dobriyan , Steven Rostedt , Peter Zijlstra , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Petr Mladek , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , Kees Cook , "Eric W. Biederman" , Greg Ungerer , Geert Uytterhoeven , Mike Rapoport , Vlastimil Babka , Vincenzo Frascino , Chinwen Chang , Michel Lespinasse , Catalin Marinas , "Matthew Wilcox (Oracle)" , Huang Ying , Jann Horn , Feng Tang , Kevin Brodsky , Michael Ellerman , Shawn Anastasio , Steven Price , Nicholas Piggin , Christian Brauner , Jens Axboe , Gabriel Krisman Bertazi , Peter Xu , Suren Baghdasaryan , Shakeel Butt , Marco Elver , Daniel Jordan , Nicolas Viennot , Thomas Cedeno , Collin Fijalkovich , Michal Hocko , Miklos Szeredi , Chengguang Xu , =?utf-8?q?Christian_K=C3=B6nig?= , linux-unionfs@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v1 4/7] binfmt: remove in-tree usage of MAP_DENYWRITE Date: Thu, 12 Aug 2021 10:43:45 +0200 Message-Id: <20210812084348.6521-5-david@redhat.com> In-Reply-To: <20210812084348.6521-1-david@redhat.com> References: <20210812084348.6521-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org At exec time when we mmap the new executable via MAP_DENYWRITE we have it opened via do_open_execat() and already deny_write_access()'ed the file successfully. Once exec completes, we allow_write_acces(); however, we set mm->exe_file in begin_new_exec() via set_mm_exe_file() and also deny_write_access() as long as mm->exe_file remains set. We'll effectively deny write access to our executable via mm->exe_file until mm->exe_file is changed -- when the process is removed, on new exec, or via sys_prctl(PR_SET_MM_EXE_FILE). Let's remove all usage of MAP_DENYWRITE, it's no longer necessary for mm->exe_file. In case of an elf interpreter, we'll now only deny write access to the file during exec. This is somewhat okay, because the interpreter behaves (and sometime is) a shared library; all shared libraries, especially the ones loaded directly in user space like via dlopen() won't ever be mapped via MAP_DENYWRITE, because we ignore that from user space completely; these shared libraries can always be modified while mapped and executed. Let's only special-case the main executable, denying write access while being executed by a process. This can be considered a minor user space visible change. While this is a cleanup, it also fixes part of a problem reported with VM_DENYWRITE on overlayfs, as VM_DENYWRITE is effectively unused with this patch and will be removed next: "Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE mappings." [1] [1] https://lore.kernel.org/r/YNHXzBgzRrZu1MrD@miu.piliscsaba.redhat.com/ Reported-by: Chengguang Xu Signed-off-by: David Hildenbrand --- arch/x86/ia32/ia32_aout.c | 6 ++---- fs/binfmt_aout.c | 5 ++--- fs/binfmt_elf.c | 4 ++-- fs/binfmt_elf_fdpic.c | 2 +- 4 files changed, 7 insertions(+), 10 deletions(-) diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c index 321d7b22ad2d..9bd15241fadb 100644 --- a/arch/x86/ia32/ia32_aout.c +++ b/arch/x86/ia32/ia32_aout.c @@ -202,8 +202,7 @@ static int load_aout_binary(struct linux_binprm *bprm) error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text, PROT_READ | PROT_EXEC, - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | - MAP_32BIT, + MAP_FIXED | MAP_PRIVATE | MAP_32BIT, fd_offset); if (error != N_TXTADDR(ex)) @@ -211,8 +210,7 @@ static int load_aout_binary(struct linux_binprm *bprm) error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data, PROT_READ | PROT_WRITE | PROT_EXEC, - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | - MAP_32BIT, + MAP_FIXED | MAP_PRIVATE | MAP_32BIT, fd_offset + ex.a_text); if (error != N_DATADDR(ex)) return error; diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c index d29de971d3f3..a47496d0f123 100644 --- a/fs/binfmt_aout.c +++ b/fs/binfmt_aout.c @@ -221,8 +221,7 @@ static int load_aout_binary(struct linux_binprm * bprm) } error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text, - PROT_READ | PROT_EXEC, - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE, + PROT_READ | PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd_offset); if (error != N_TXTADDR(ex)) @@ -230,7 +229,7 @@ static int load_aout_binary(struct linux_binprm * bprm) error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data, PROT_READ | PROT_WRITE | PROT_EXEC, - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE, + MAP_FIXED | MAP_PRIVATE, fd_offset + ex.a_text); if (error != N_DATADDR(ex)) return error; diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 6d2c79533631..69d900a8473d 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -622,7 +622,7 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex, eppnt = interp_elf_phdata; for (i = 0; i < interp_elf_ex->e_phnum; i++, eppnt++) { if (eppnt->p_type == PT_LOAD) { - int elf_type = MAP_PRIVATE | MAP_DENYWRITE; + int elf_type = MAP_PRIVATE; int elf_prot = make_prot(eppnt->p_flags, arch_state, true, true); unsigned long vaddr = 0; @@ -1070,7 +1070,7 @@ static int load_elf_binary(struct linux_binprm *bprm) elf_prot = make_prot(elf_ppnt->p_flags, &arch_state, !!interpreter, false); - elf_flags = MAP_PRIVATE | MAP_DENYWRITE; + elf_flags = MAP_PRIVATE; vaddr = elf_ppnt->p_vaddr; /* diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index cf4028487dcc..6d8fd6030cbb 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -1041,7 +1041,7 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params, if (phdr->p_flags & PF_W) prot |= PROT_WRITE; if (phdr->p_flags & PF_X) prot |= PROT_EXEC; - flags = MAP_PRIVATE | MAP_DENYWRITE; + flags = MAP_PRIVATE; maddr = 0; switch (params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) {