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Fri, 17 Feb 2023 10:56:16 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1676631379; bh=0cm+6yx0egHzCd1QYH/vCS5/vaBg8Fj6bVNYndgzW+0=; h=From:To:Cc:Subject:Date:From; b=Q0llhFTdI6/tcyIlD65gdzZxHM/rtq/TPPB4qZdjwFH0fWwTldJHYaRV93E4zP1+F E9bqb5P7I7VqBHbCYnjb3j4536wu1MaltQGuS7f8QWmr1iCw/3lr8jYEj4+OFRBBDG /rWPZCUFnBxIoFXTb+1qdlQGfqKLf12c/4p1kdGIQ4/WunzsoJDzlkPGBj6wHyzB5X PgWEbS/PXtaViLq6msS+F9a27gclSWwZHskdeZ0PfW3GSZ8l34pdfZZCEqLrXqRGGO GufqWl8APPHtTAUOK+EQ43ecAd82DvjV0fgqRmye0kMuXEaLpsxJnY7BQiKt4VJYsv +f/42e54O1HeA== 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 v5] mm/userfaultfd: Support WP on multiple VMAs Date: Fri, 17 Feb 2023 15:55:58 +0500 Message-Id: <20230217105558.832710-1-usama.anjum@collabora.com> X-Mailer: git-send-email 2.39.1 MIME-Version: 1.0 X-Rspamd-Queue-Id: 1FCE9C0015 X-Stat-Signature: znwzyciwm6n1nohtdgpzoxwtz13n3hgd X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1676631380-511680 X-HE-Meta: U2FsdGVkX1+2+6hN4p4ZvMNQhFOlZ3Wd+BlW48+wdiHhfI03Mu4j5/neSnhKJPbKdH0AYgBh/hyiIJf0IY8lxlTSUQpI4eKrwCyRxPiWtab5rGS6a7sBsvtsH8UlreE1KOgfTEq+yzCNug2zPLOkEZTyVHUmgX5/uAZibUkRnrwzq8vjIgzjKIbhy+3+OgDFL1+Ailb5J+MVs1aZh4Ot7o6JA7CKhyFKI3YVAsnjioPF3XeQ2A7XzW0PAUSGZ3WutEeytSgornv5xLa5qPn+IMCxyB164oHOuv/ktacvr/Z/SVuSfQ3NjoAIXKXDVbrwiIdL8jka+vb+A6Uzrwn7nH/uI3Mbai5H6a4J2SuOVt5l/JHF/7JKFbTDYyjLpC0QMRMg7hmkqNe8FxuCMrvv6xotXsdZeCkxiDCDS+Jrbxh1YfqWTK0Xuc91WFuc/A3x+FgH49vhK9XElXWr0c1o8Yl8bo/s9CIs0tDAVVPCZgdqOjv1qKxqzuAwtlF3Dy/HTV5p1apHPKAhxp26W9sMjko9zJFZFRcMBkJn9v9o781FGKO28mFCbMiynv4NTg23bUoUGKenyrUys9mwHZ0nH1n9UBcFJf1MMGyQVzen6VyZHjX7s5aW6tTwVuxp/P3VjezzpVID6jtf4AY12mBwdp6qf87X6UKCiAFAC5zuAqEMmHPbE+OgKJGI7fCzTr3HGiy6M4gRIyrMn4PhfawUtoHNuH2CVxswtIlgzEDIPw9nfa+KAq8LS6L223kMRo0g+Ai2PZTuHfmLFOytu8XZZtPcU3Pn1GKQ6BJkOorDbCmG4DOUQzHPKUcIJTm/+wepcKFcDCWlA3UDvDfwXLxiQNJBhYFkjx1kwXlCtX0O4oFtGh+B1pMEPpg0AR8enSR7IYXwVKYGromNrkuOBZrdEZ7DRUXxAk2Bvpaky2CUi7luabeEQiTf4TQs/w0MEMC0LiTWkrbH20xqEhGgGqh cZyDbDTi EhuDeGVU6y0EqKQGp735shl+kipMcJElQblsSj5MNDL3n5nw9v94kfN9wYB5MNMf7ZH1kmajVL5ZLmNmmU4uAwRb3PiBAUXUt5OQWcD7gDOUqreG4LzDLcl9jlgrLguYt4KGNgGCZcXYjaOJpM2zqu8P8AAz6pzSuc2rqg14HsSDT2orS16KYQ2blV9aiHvQL+R5gdcaU7QVVlE5BiV7yuswnsIsqXnUaMS9WpEpd/qy1ainU/PVBWYrNrgfivF98neFzPH2R16zgoevpvLC67RNmdLT13XugRi30WyiudqAzoa9/lajwMHV+64iGG/zXyHorzyQCtqXtrimG9mC3PkpurQ== 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. Acked-by: Peter Xu Acked-by: David Hildenbrand Reported-by: Paul Gofman Signed-off-by: Muhammad Usama Anjum --- Changes since v4: - Merge two separate patches and convert VM_WARN_ON() to VM_WARN_ON_ONCE() - Update commit description and add tags 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 | 41 ++++++++++++++++++++++++----------------- 1 file changed, 24 insertions(+), 17 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 53c3d916ff66..9057648248e7 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -717,6 +717,8 @@ long uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma, struct mmu_gather tlb; long ret; + VM_WARN_ON_ONCE(start < dst_vma->vm_start || start + len > dst_vma->vm_end, + "The address range exceeds VMA boundary.\n"); if (enable_wp) mm_cp_flags = MM_CP_UFFD_WP; else @@ -741,9 +743,12 @@ 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 +771,30 @@ 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;