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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 A249BC4338F for ; Thu, 19 Aug 2021 20:52:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8108B610A0 for ; Thu, 19 Aug 2021 20:52:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235584AbhHSUw7 (ORCPT ); Thu, 19 Aug 2021 16:52:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48570 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235810AbhHSUw6 (ORCPT ); Thu, 19 Aug 2021 16:52:58 -0400 Received: from mail-ed1-x534.google.com (mail-ed1-x534.google.com [IPv6:2a00:1450:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A81BC06175F for ; Thu, 19 Aug 2021 13:52:21 -0700 (PDT) Received: by mail-ed1-x534.google.com with SMTP id i6so10772509edu.1 for ; Thu, 19 Aug 2021 13:52:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RJyUMpRvCKY0Vh89D3w3gONjiQnSaoV/zmqyDYmDpUA=; b=Y+pU8j9vQaWTxEhQ0j0tkQUmizFhaaD+mBD4UKDchtCcNJDPjhu50XdOkmR7wRhVkU sO/ZAyNE37DjaIrX3Jupm5Lmzorw4l3UwqrPdvdUzj38oBpjeDPsJPwAdFT5IzBfsdoc aflzICp2BeWzdnFJvaqwcQw0cXI2edPGK5Q7U= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RJyUMpRvCKY0Vh89D3w3gONjiQnSaoV/zmqyDYmDpUA=; b=ZBY69WTqnwgzo0ndX8HISQRpORr9FiMhXktHtbVif7W/3mtaklOp4GIKUVFCkEtfhj OEe+Rqlil2RcHWbB1P87Df7Sb7X9MF6jhBs3an1bZbByqA06WzIN9Z2d7CIN3OJIUFWj cPXm2GhoUynRa5RTAEkoDNNnsCHs+rmTIv1b8NEQDxYmpyooiWk2HSS8dWTJ+WSFTuTr tTt+zyeu77fGjldoZN6eMUKo0pniDf59bVUu1FmEMMfDrESdrjB5IVQOymkGsJ8k84oe WUa7KV8wzn5z+4Y/RqDTkjjKkSivg+RXKWC11aDQY+aawrkd5SYEA0LL+m8ZQrZQFGej Ntbg== X-Gm-Message-State: AOAM530iWKg5c5bNzGq3YhcpVA2aV4DiOnKxVtWP0lSzA1eiDTRoF5Ou AhCPjvQMZRZNoWnto0aMDVufLVzgLRCwEM23SMk= X-Google-Smtp-Source: ABdhPJxXWfhd+VyWq8lHAXc7VzIdF0woajX4gt/AaR9kqc25TM0B3Gs/1O3b+6mBS6+OODPkYaHDhw== X-Received: by 2002:a05:6402:394:: with SMTP id o20mr18185897edv.232.1629406339672; Thu, 19 Aug 2021 13:52:19 -0700 (PDT) Received: from mail-ej1-f54.google.com (mail-ej1-f54.google.com. [209.85.218.54]) by smtp.gmail.com with ESMTPSA id n13sm1766046ejk.97.2021.08.19.13.52.17 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Aug 2021 13:52:18 -0700 (PDT) Received: by mail-ej1-f54.google.com with SMTP id d11so15458378eja.8 for ; Thu, 19 Aug 2021 13:52:17 -0700 (PDT) X-Received: by 2002:a19:4f1a:: with SMTP id d26mr11559422lfb.377.1629406326706; Thu, 19 Aug 2021 13:52:06 -0700 (PDT) MIME-Version: 1.0 References: <20210816194840.42769-1-david@redhat.com> <20210816194840.42769-3-david@redhat.com> In-Reply-To: <20210816194840.42769-3-david@redhat.com> From: Linus Torvalds Date: Thu, 19 Aug 2021 13:51:50 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 2/7] kernel/fork: factor out replacing the current MM exe_file To: David Hildenbrand Cc: Linux Kernel Mailing List , 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 , 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 , Michal Hocko , Miklos Szeredi , Chengguang Xu , =?UTF-8?Q?Christian_K=C3=B6nig?= , Florian Weimer , David Laight , linux-unionfs@vger.kernel.org, Linux API , "the arch/x86 maintainers" , linux-fsdevel , Linux-MM Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org So I like this series. However, logically, I think this part in replace_mm_exe_file() no longer makes sense: On Mon, Aug 16, 2021 at 12:50 PM David Hildenbrand wrote: > > + /* Forbid mm->exe_file change if old file still mapped. */ > + old_exe_file = get_mm_exe_file(mm); > + if (old_exe_file) { > + mmap_read_lock(mm); > + for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) { > + if (!vma->vm_file) > + continue; > + if (path_equal(&vma->vm_file->f_path, > + &old_exe_file->f_path)) > + ret = -EBUSY; > + } > + mmap_read_unlock(mm); > + fput(old_exe_file); > + if (ret) > + return ret; > + } and should just be removed. NOTE! I think it makes sense within the context of this patch (where you just move code around), but that it should then be removed in the next patch that does that "always deny write access to current MM exe_file" thing. I just quoted it in the context of this patch, since the next patch doesn't actually show this code any more. In the *old* model - where the ETXTBUSY was about the mmap() of the file - the above tests make sense. But in the new model, walking the mappings just doesn't seem to be a sensible operation any more. The mappings simply aren't what ETXTBUSY is about in the new world order, and so doing that mapping walk seems nonsensical. Hmm? Linus