From patchwork Sun Apr 30 22:26:05 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lorenzo Stoakes X-Patchwork-Id: 13227327 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B441EC7EE25 for ; Sun, 30 Apr 2023 22:26:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232070AbjD3W0r (ORCPT ); Sun, 30 Apr 2023 18:26:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232062AbjD3W0p (ORCPT ); Sun, 30 Apr 2023 18:26:45 -0400 Received: from mail-wm1-x32a.google.com (mail-wm1-x32a.google.com [IPv6:2a00:1450:4864:20::32a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2C841A8; Sun, 30 Apr 2023 15:26:43 -0700 (PDT) Received: by mail-wm1-x32a.google.com with SMTP id 5b1f17b1804b1-3f09b4a1584so10641415e9.2; Sun, 30 Apr 2023 15:26:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1682893602; x=1685485602; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Yb73uisocFKIniSChsToEe21gb62ZyaVkxC6mK3mItE=; b=gsFUOW0Y9mVkXYV4t1E3PZo4X+N6fp7jxDS8tKbqlcgdlkmj2YG0RghKtdWI4BHcOn xmp8KAt5xli9RCnbEdUVxSSUWCGjy24PH09/PdiiJh7jpjCgPLpX2EhIJuaszKUJClIO yUPl5VmCgoUzeb6EVEGupAsJVFpMsZGFY8XhBfz7ERKU5+CTzb/dsrItI8T4HkBJZvd3 jglAD7KNqidPxalMHaS4SSmu+1+R2DLYIOztB9CPpdBc4DkwwKFLL1a/QyUKGiikRpE0 z8rsTAmdz1M0ur6TcRjjdsphLB3CeA9C+VoFBwIAfT4upypl8VdTAVrSyVvooMoXErfV /n0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1682893602; x=1685485602; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Yb73uisocFKIniSChsToEe21gb62ZyaVkxC6mK3mItE=; b=ilAivtNeVo8LZusXWj3IL1/TCSdVMrTkvaltR8wiamqysfzkQGXmL0dDhvMO9dErl7 NBlwglQBfNt5tY9/DPIlBxlLH9l84XxpTVPZMZZOBZEJ3NXe5C6bBpA1a6RMwdJCtqh9 qcS9AT6p8JjxwjkRQC1gMy/uiqzl8j5qp4zTH2v9j04+sWqMIMlQp1tut7u3cx5+cCRM XjumUH0IYJPXVYHKg8s7K4ZXoJDbuKRVTcW0emX7dYuQasFtzXXi7qJVSk3LBHYOdXxP /VgMNrkskja2ZT82uHjZ1t9ZdXtZWhEaI3JmuddTkbcZlQfbN2WXw7LfxaFh5Bwc+PGz YpDw== X-Gm-Message-State: AC+VfDxyOCgQOY9Y/bU4kwd+uTUIxXAOm/4nHS2mwm09hSoYjZ/yATK8 Lzs/5jeIQrTtxS8aDn9Mw/E= X-Google-Smtp-Source: ACHHUZ57BxNNYDj7zctg3JHwhr5cvQ58P7G8J8BYjVMfhqIVRLA7nj5p4p4AxNhjquz50+Pn+mUt6A== X-Received: by 2002:a5d:40c4:0:b0:306:2b1a:101d with SMTP id b4-20020a5d40c4000000b003062b1a101dmr2146028wrq.12.1682893602232; Sun, 30 Apr 2023 15:26:42 -0700 (PDT) Received: from lucifer.home ([2a00:23c5:dc8c:8701:1663:9a35:5a7b:1d76]) by smtp.googlemail.com with ESMTPSA id g2-20020a5d5402000000b002da75c5e143sm26699865wrv.29.2023.04.30.15.26.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Apr 2023 15:26:41 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Cc: Matthew Wilcox , Mike Kravetz , Muchun Song , Alexander Viro , Christian Brauner , Andy Lutomirski , linux-fsdevel@vger.kernel.org, Jan Kara , Hugh Dickins , Lorenzo Stoakes Subject: [PATCH v2 1/3] mm: drop the assumption that VM_SHARED always implies writable Date: Sun, 30 Apr 2023 23:26:05 +0100 Message-Id: X-Mailer: git-send-email 2.40.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org There are places in the kernel where there is an implicit assumption that VM_SHARED VMAs must either be writable or might become writable via e.g. mprotect(). We can explicitly check for the writable, shared case while remaining conservative - If VM_MAYWRITE is not set then, by definition, the memory can never be written to. Update these checks to also check for VM_MAYWRITE. Suggested-by: Andy Lutomirski Signed-off-by: Lorenzo Stoakes --- include/linux/fs.h | 4 ++-- include/linux/mm.h | 11 +++++++++++ kernel/fork.c | 2 +- mm/filemap.c | 2 +- mm/madvise.c | 2 +- mm/mmap.c | 12 ++++++------ 6 files changed, 22 insertions(+), 11 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index 67495ef79bb2..874fe0e38e65 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -413,7 +413,7 @@ extern const struct address_space_operations empty_aops; * It is also used to block modification of page cache contents through * memory mappings. * @gfp_mask: Memory allocation flags to use for allocating pages. - * @i_mmap_writable: Number of VM_SHARED mappings. + * @i_mmap_writable: Number of VM_SHARED, VM_MAYWRITE mappings. * @nr_thps: Number of THPs in the pagecache (non-shmem only). * @i_mmap: Tree of private and shared mappings. * @i_mmap_rwsem: Protects @i_mmap and @i_mmap_writable. @@ -516,7 +516,7 @@ static inline int mapping_mapped(struct address_space *mapping) /* * Might pages of this file have been modified in userspace? - * Note that i_mmap_writable counts all VM_SHARED vmas: do_mmap + * Note that i_mmap_writable counts all VM_SHARED, VM_MAYWRITE vmas: do_mmap * marks vma as VM_SHARED if it is shared, and the file was opened for * writing i.e. vma may be mprotected writable even if now readonly. * diff --git a/include/linux/mm.h b/include/linux/mm.h index 27ce77080c79..3e8fb4601520 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -851,6 +851,17 @@ static inline bool vma_is_accessible(struct vm_area_struct *vma) return vma->vm_flags & VM_ACCESS_FLAGS; } +static inline bool is_shared_maywrite(vm_flags_t vm_flags) +{ + return (vm_flags & (VM_SHARED | VM_MAYWRITE)) == + (VM_SHARED | VM_MAYWRITE); +} + +static inline bool vma_is_shared_maywrite(struct vm_area_struct *vma) +{ + return is_shared_maywrite(vma->vm_flags); +} + static inline struct vm_area_struct *vma_find(struct vma_iterator *vmi, unsigned long max) { diff --git a/kernel/fork.c b/kernel/fork.c index 4342200d5e2b..7ebd6229219a 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -733,7 +733,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, get_file(file); i_mmap_lock_write(mapping); - if (tmp->vm_flags & VM_SHARED) + if (vma_is_shared_maywrite(tmp)) mapping_allow_writable(mapping); flush_dcache_mmap_lock(mapping); /* insert tmp into the share list, just after mpnt */ diff --git a/mm/filemap.c b/mm/filemap.c index a34abfe8c654..4d896515032c 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3607,7 +3607,7 @@ int generic_file_mmap(struct file *file, struct vm_area_struct *vma) */ int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) { - if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) + if (vma_is_shared_maywrite(vma)) return -EINVAL; return generic_file_mmap(file, vma); } diff --git a/mm/madvise.c b/mm/madvise.c index b5ffbaf616f5..5eb59854e285 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -969,7 +969,7 @@ static long madvise_remove(struct vm_area_struct *vma, return -EINVAL; } - if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE)) + if (!vma_is_shared_maywrite(vma)) return -EACCES; offset = (loff_t)(start - vma->vm_start) diff --git a/mm/mmap.c b/mm/mmap.c index 5522130ae606..646e34e95a37 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -107,7 +107,7 @@ void vma_set_page_prot(struct vm_area_struct *vma) static void __remove_shared_vm_struct(struct vm_area_struct *vma, struct file *file, struct address_space *mapping) { - if (vma->vm_flags & VM_SHARED) + if (vma_is_shared_maywrite(vma)) mapping_unmap_writable(mapping); flush_dcache_mmap_lock(mapping); @@ -428,7 +428,7 @@ static unsigned long count_vma_pages_range(struct mm_struct *mm, static void __vma_link_file(struct vm_area_struct *vma, struct address_space *mapping) { - if (vma->vm_flags & VM_SHARED) + if (vma_is_shared_maywrite(vma)) mapping_allow_writable(mapping); flush_dcache_mmap_lock(mapping); @@ -2642,7 +2642,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, vma->vm_pgoff = pgoff; if (file) { - if (vm_flags & VM_SHARED) { + if (is_shared_maywrite(vm_flags)) { error = mapping_map_writable(file->f_mapping); if (error) goto free_vma; @@ -2717,7 +2717,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, vma_iter_store(&vmi, vma); mm->map_count++; if (vma->vm_file) { - if (vma->vm_flags & VM_SHARED) + if (vma_is_shared_maywrite(vma)) mapping_allow_writable(vma->vm_file->f_mapping); flush_dcache_mmap_lock(vma->vm_file->f_mapping); @@ -2734,7 +2734,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, /* Once vma denies write, undo our temporary denial count */ unmap_writable: - if (file && vm_flags & VM_SHARED) + if (file && is_shared_maywrite(vm_flags)) mapping_unmap_writable(file->f_mapping); file = vma->vm_file; ksm_add_vma(vma); @@ -2781,7 +2781,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start, vma->vm_end, true); } - if (file && (vm_flags & VM_SHARED)) + if (file && is_shared_maywrite(vm_flags)) mapping_unmap_writable(file->f_mapping); free_vma: vm_area_free(vma);