From patchwork Thu Feb 16 09:16:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Muhammad Usama Anjum X-Patchwork-Id: 13142745 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8C3E7C61DA4 for ; Thu, 16 Feb 2023 09:17:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 265846B0071; Thu, 16 Feb 2023 04:17:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 214DD6B0072; Thu, 16 Feb 2023 04:17:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0DD0A6B0073; Thu, 16 Feb 2023 04:17:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id F06436B0071 for ; 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Thu, 16 Feb 2023 09:17:14 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1676539037; bh=p4O0JNqalB3DAfjfajI/CREv4U82nvTHiokxTLoKpk8=; h=From:To:Cc:Subject:Date:From; b=XU1WgQCRSsJY1e29r6FI2zJEyv/jAz6OCElh7uJFm7MQQsehZiLzQxp4UOkuiD890 t0/pMZ7ivUSue7NYar66RJl2AkCmiY1rfDSLlRR2WHg+lZRipo9nfTsQY6bjMZqDGM h92lTZ6S/8Cyk9YRp0P4d1HL0Jr50gxW6KRtYmIrtTCzJgnh6BbsuN7FqF4cb9m9kE bdV2t1q+2TErvBlTpjw72dJy2pHXHJkOS74depQNWhQtvjQIguNxgmsoYLSjy5+7jP r7WqQZbiKXbLrLnyRodnotGJCmUA68KBF348rmo5u8rktY+0/LYzVEzsCzSgzOJsug ajRGcznHfbDHg== From: Muhammad Usama Anjum To: peterx@redhat.com, david@redhat.com, Andrew Morton Cc: Muhammad Usama Anjum , kernel@collabora.com, Paul Gofman , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 1/2] mm/userfaultfd: Support WP on multiple VMAs Date: Thu, 16 Feb 2023 14:16:55 +0500 Message-Id: <20230216091656.2045471-1-usama.anjum@collabora.com> X-Mailer: git-send-email 2.39.1 MIME-Version: 1.0 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: D4F04140012 X-Rspam-User: X-Stat-Signature: fqxrzcq9ucdhzwr53ktkftab54ieg56k X-HE-Tag: 1676539038-372441 X-HE-Meta: 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 /LpbSm2C f74z8dQYQwKBpbFn4aJvjYfebPXkaGJ7nYzmw2fOaIZy/a2+fhEMcH0M3OU1c6ZU0aB/XzuVnB1rl/4CXrEnuZ1RopCj23PMGgcWtx32c4bmxBpkuS7Q67TcBVwFcmT7aZst9ALlYxMcT3LnXxJ6Y1/CBVTDvYrE1HozirjL+UFTEzUcAGP2XJYHOii4D5nnZFAiZ9P/6LtnPRBDVRYRUTQV/0pOf4hMr8J7qyJChIPObAr1ynBCCo0xYpZEu5UjA+jbQZLkeaNzJEhQ1vuRXw7VqgFxoejyuc3xTpQCTTBB3Gbt/gWTPsIi6NGwzX++X4L3C X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: mwriteprotect_range() errors out if [start, end) doesn't fall in one VMA. We are facing a use case where multiple VMAs are present in one range of interest. For example, the following pseudocode reproduces the error which we are trying to fix: - Allocate memory of size 16 pages with PROT_NONE with mmap - Register userfaultfd - Change protection of the first half (1 to 8 pages) of memory to PROT_READ | PROT_WRITE. This breaks the memory area in two VMAs. - Now UFFDIO_WRITEPROTECT_MODE_WP on the whole memory of 16 pages errors out. This is a simple use case where user may or may not know if the memory area has been divided into multiple VMAs. We need an implementation which doesn't disrupt the already present users. So keeping things simple, stop going over all the VMAs if any one of the VMA hasn't been registered in WP mode. While at it, remove the un-needed error check as well. Reported-by: Paul Gofman Signed-off-by: Muhammad Usama Anjum Acked-by: David Hildenbrand Acked-by: Peter Xu --- Changes since v3: - Rebase on top of next-20230616 Changes since v2: - Correct the return error code and cleanup a bit Changes since v1: - Correct the start and ending values passed to uffd_wp_range() --- mm/userfaultfd.c | 39 ++++++++++++++++++++++----------------- 1 file changed, 22 insertions(+), 17 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 53c3d916ff66..77c5839e591c 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -741,9 +741,12 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, unsigned long len, bool enable_wp, atomic_t *mmap_changing) { + unsigned long end = start + len; + unsigned long _start, _end; struct vm_area_struct *dst_vma; unsigned long page_mask; long err; + VMA_ITERATOR(vmi, dst_mm, start); /* * Sanitize the command parameters: @@ -766,28 +769,30 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, goto out_unlock; err = -ENOENT; - dst_vma = find_dst_vma(dst_mm, start, len); + for_each_vma_range(vmi, dst_vma, end) { - if (!dst_vma) - goto out_unlock; - if (!userfaultfd_wp(dst_vma)) - goto out_unlock; - if (!vma_can_userfault(dst_vma, dst_vma->vm_flags)) - goto out_unlock; + if (!userfaultfd_wp(dst_vma)) { + err = -ENOENT; + break; + } - if (is_vm_hugetlb_page(dst_vma)) { - err = -EINVAL; - page_mask = vma_kernel_pagesize(dst_vma) - 1; - if ((start & page_mask) || (len & page_mask)) - goto out_unlock; - } + if (is_vm_hugetlb_page(dst_vma)) { + err = -EINVAL; + page_mask = vma_kernel_pagesize(dst_vma) - 1; + if ((start & page_mask) || (len & page_mask)) + break; + } - err = uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); + _start = max(dst_vma->vm_start, start); + _end = min(dst_vma->vm_end, end); - /* Return 0 on success, <0 on failures */ - if (err > 0) - err = 0; + err = uffd_wp_range(dst_mm, dst_vma, _start, _end - _start, enable_wp); + /* Return 0 on success, <0 on failures */ + if (err < 0) + break; + err = 0; + } out_unlock: mmap_read_unlock(dst_mm); return err;