From patchwork Thu Feb 16 06:41:54 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: 13142663 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 7A8D5C61DA4 for ; Thu, 16 Feb 2023 06:42:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C29BA6B0078; Thu, 16 Feb 2023 01:42:25 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BD9586B007B; Thu, 16 Feb 2023 01:42:25 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AA0EF6B007D; Thu, 16 Feb 2023 01:42:25 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 9A8486B0078 for ; 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Thu, 16 Feb 2023 06:42:19 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1676529742; bh=BZYuBCeCugmy4mw2Nhoe/U7I5Z6mqKYkAE3a/WqYnEQ=; h=From:To:Cc:Subject:Date:From; b=GkeuNID2I8NnX4wJVAJsXUfQkgPZyOZKR+eVujKQ09Y3AbRJ8FZFsN7U4ooRlFFoZ fnP8+JZOMcVFRime6Bov4K9XY1mBpR2qjfvkn0FL+V4g3HERnBXL+j0SdLBjjQwFIl kmvRMnoOawcDoN9e2RConX+4bvsTyXBuh2TDMn5Om4sh2RVYW+IJHUj2cGdy5xJQK5 GfakwV3k9bfLmv9AWttXoGO6OGGiNqcVikmBrEWpJDPyFTuv2Kdo/ml5+Q5N2fO6Zw 34DTtYe+HXIidPiVZ7VQ0SYA/GE/ORWBCeMwhD0GfwYNrNZ3lbqgPJ0tCyDk9+G/+w lLZyOC26N2LGw== 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 v3 1/2] mm/userfaultfd: Support WP on multiple VMAs Date: Thu, 16 Feb 2023 11:41:54 +0500 Message-Id: <20230216064155.1500545-1-usama.anjum@collabora.com> X-Mailer: git-send-email 2.39.1 MIME-Version: 1.0 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: ADAD340007 X-Stat-Signature: rsmaa1pupu5g1ak1sdneouy7w97yjgwx X-Rspam-User: X-HE-Tag: 1676529743-721684 X-HE-Meta: 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 e+Dx7y6X jZAYffk36QKDxT5xnBM6Ucck0q++vfamVb7WSliP/pt/ThKQNfX4+dSCsFiEy6kgjHbHqtOq3HBRCej8CCLvo4elyE3YuESZDQs68eKWtvZErdC1kfM79zQFW/Sj4DkGeJjsa2F7w1kvY3+/Oth+ySr11iNBO8ACW9Nu9dAatyGY8KKRSwMQ4GxbwRxlPSc8vmTdNxIbY120jqny71HcKaYb3dWOztxHiTv3oYeXDAFpspjDo3pwgFsJZDNpVSmRb9dVW8S17lBG2BImtn9GODWa5k0Q/OMGFKfs42g8YGFGOAnGNno35rnogueYYpYCGLidh 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 --- 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 | 35 ++++++++++++++++++++--------------- 1 file changed, 20 insertions(+), 15 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 65ad172add27..366dc097ab11 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -738,9 +738,12 @@ 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; int err; + VMA_ITERATOR(vmi, dst_mm, start); /* * Sanitize the command parameters: @@ -763,25 +766,27 @@ 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; + } + + _start = max(dst_vma->vm_start, start); + _end = min(dst_vma->vm_end, end); - uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); + uffd_wp_range(dst_mm, dst_vma, _start, _end - _start, enable_wp); - err = 0; + err = 0; + } out_unlock: mmap_read_unlock(dst_mm); return err;