From patchwork Thu Aug 12 08:43:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12432887 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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 4505BC432BE for ; Thu, 12 Aug 2021 08:44:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 291416103A for ; Thu, 12 Aug 2021 08:44:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234600AbhHLIop (ORCPT ); Thu, 12 Aug 2021 04:44:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:26338 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234153AbhHLIol (ORCPT ); Thu, 12 Aug 2021 04:44:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628757855; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=M39zbsaS2KZL2Rdtv+g1mE9Yxte2yzqnEHMfKrq3Rbk=; b=ZcN8zeGKG/MKsCYKJKQovLb1bz2A4nFqk+DPisr8h3ZU4eos2q/25ecsPIM6PXm9XVo8hn 2muxYOUfYIoPiK5t4urKE4uGaWFyfGGWRqS/5ZWywwyXmdANLYSlqzTTVpoRlMda772J/O UFJAjasbxEd9oJLqLwtjdAqnGr0hV7Q= 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-17-7fdL4v-iM_6gXav43YmE2Q-1; Thu, 12 Aug 2021 04:44:13 -0400 X-MC-Unique: 7fdL4v-iM_6gXav43YmE2Q-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 3DDF21082926; Thu, 12 Aug 2021 08:44:12 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.193.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id C18B05C23A; Thu, 12 Aug 2021 08:43:49 +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 0/7] Remove in-tree usage of MAP_DENYWRITE Date: Thu, 12 Aug 2021 10:43:41 +0200 Message-Id: <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 This series is based on v5.14-rc5 and corresponds code-wise to the previously sent RFC [1] (the RFC still applied cleanly). This series removes all in-tree usage of MAP_DENYWRITE from the kernel and removes VM_DENYWRITE. We stopped supporting MAP_DENYWRITE for user space applications a while ago because of the chance for DoS. The last renaming user is binfmt binary loading during exec and legacy library loading via uselib(). With this change, MAP_DENYWRITE is effectively ignored throughout the kernel. Although the net change is small, I think the cleanup in mmap() is quite nice. There are some (minor) user-visible changes with this series: 1. We no longer deny write access to shared libaries loaded via legacy uselib(); this behavior matches modern user space e.g., via dlopen(). 2. We no longer deny write access to the elf interpreter after exec completed, treating it just like shared libraries (which it often is). 3. We always deny write access to the file linked via /proc/pid/exe: sys_prctl(PR_SET_MM_EXE_FILE) will fail if write access to the file cannot be denied, and write access to the file will remain denied until the link is effectivel gone (exec, termination, PR_SET_MM_EXE_FILE) -- just as if exec'ing the file. I was wondering if we really care about permanently disabling write access to the executable, or if it would be good enough to just disable write access while loading the new executable during exec; but I don't know the history of that -- and it somewhat makes sense to deny write access at least to the main executable. With modern user space -- dlopen() -- we can effectively modify the content of shared libraries while being used. There is a related problem [2] with overlayfs, that should at least partly be tackled by this series. I don't quite understand the interaction of overlayfs and deny_write_access()/allow_write_access() at exec time: If we end up denying write access to the wrong file and not to the realfile, that would be fundamentally broken. We would have to reroute our deny_write_access()/ allow_write_access() calls for the exec file to the realfile -- but I leave figuring out the details to overlayfs guys, as that would be a related but different issue. RFC -> v1: - "binfmt: remove in-tree usage of MAP_DENYWRITE" -- Add a note that this should fix part of a problem with overlayfs [1] https://lore.kernel.org/r/20210423131640.20080-1-david@redhat.com/ [2] https://lore.kernel.org/r/YNHXzBgzRrZu1MrD@miu.piliscsaba.redhat.com/ Cc: Linus Torvalds Cc: Andrew Morton Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: Alexander Viro Cc: Alexey Dobriyan Cc: Steven Rostedt Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Mark Rutland Cc: Alexander Shishkin Cc: Jiri Olsa Cc: Namhyung Kim Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Andy Shevchenko Cc: Rasmus Villemoes Cc: Kees Cook Cc: "Eric W. Biederman" Cc: Greg Ungerer Cc: Geert Uytterhoeven Cc: Mike Rapoport Cc: Vlastimil Babka Cc: Vincenzo Frascino Cc: Chinwen Chang Cc: Michel Lespinasse Cc: Catalin Marinas Cc: "Matthew Wilcox (Oracle)" Cc: Huang Ying Cc: Jann Horn Cc: Feng Tang Cc: Kevin Brodsky Cc: Michael Ellerman Cc: Shawn Anastasio Cc: Steven Price Cc: Nicholas Piggin Cc: Christian Brauner Cc: Jens Axboe Cc: Gabriel Krisman Bertazi Cc: Peter Xu Cc: Suren Baghdasaryan Cc: Shakeel Butt Cc: Marco Elver Cc: Daniel Jordan Cc: Nicolas Viennot Cc: Thomas Cedeno Cc: Collin Fijalkovich Cc: Michal Hocko Cc: Miklos Szeredi Cc: Chengguang Xu Cc: "Christian König" Cc: linux-unionfs@vger.kernel.org Cc: linux-api@vger.kernel.org Cc: x86@kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org David Hildenbrand (7): binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib() kernel/fork: factor out atomcially replacing the current MM exe_file kernel/fork: always deny write access to current MM exe_file binfmt: remove in-tree usage of MAP_DENYWRITE mm: remove VM_DENYWRITE mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff() fs: update documentation of get_write_access() and friends arch/x86/ia32/ia32_aout.c | 8 ++-- fs/binfmt_aout.c | 7 ++-- fs/binfmt_elf.c | 6 +-- fs/binfmt_elf_fdpic.c | 2 +- fs/proc/task_mmu.c | 1 - include/linux/fs.h | 19 +++++---- include/linux/mm.h | 3 +- include/linux/mman.h | 4 +- include/trace/events/mmflags.h | 1 - kernel/events/core.c | 2 - kernel/fork.c | 75 ++++++++++++++++++++++++++++++---- kernel/sys.c | 33 +-------------- lib/test_printf.c | 5 +-- mm/mmap.c | 29 ++----------- mm/nommu.c | 2 - 15 files changed, 98 insertions(+), 99 deletions(-) base-commit: 36a21d51725af2ce0700c6ebcb6b9594aac658a6 Acked-by: "Eric W. Biederman"