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Shutemov" , Maya Gokhale , Johannes Weiner , Marty McFadden , Denis Plotnikov , Hugh Dickins , "Dr . David Alan Gilbert" , Jerome Glisse , Shaohua Li , Rik van Riel Subject: [PATCH v6 12/19] userfaultfd: wp: support write protection for userfault vma range Date: Thu, 20 Feb 2020 11:31:05 -0500 Message-Id: <20200220163112.11409-13-peterx@redhat.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200220163112.11409-1-peterx@redhat.com> References: <20200220163112.11409-1-peterx@redhat.com> MIME-Version: 1.0 X-MC-Unique: TSdDE94UPd2NXU9XwXXI0w-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable 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: From: Shaohua Li Add API to enable/disable writeprotect a vma range. Unlike mprotect, this doesn't split/merge vmas. Cc: Andrea Arcangeli Cc: Rik van Riel Cc: Kirill A. Shutemov Cc: Mel Gorman Cc: Hugh Dickins Cc: Johannes Weiner Signed-off-by: Shaohua Li Signed-off-by: Andrea Arcangeli [peterx: - use the helper to find VMA; - return -ENOENT if not found to match mcopy case; - use the new MM_CP_UFFD_WP* flags for change_protection - check against mmap_changing for failures - replace find_dst_vma with vma_find_uffd] Reviewed-by: Jerome Glisse Reviewed-by: Mike Rapoport Signed-off-by: Peter Xu --- include/linux/userfaultfd_k.h | 3 ++ mm/userfaultfd.c | 54 +++++++++++++++++++++++++++++++++++ 2 files changed, 57 insertions(+) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index dcd33172b728..a8e5f3ea9bb2 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -41,6 +41,9 @@ extern ssize_t mfill_zeropage(struct mm_struct *dst_mm, =09=09=09 unsigned long dst_start, =09=09=09 unsigned long len, =09=09=09 bool *mmap_changing); +extern int mwriteprotect_range(struct mm_struct *dst_mm, +=09=09=09 unsigned long start, unsigned long len, +=09=09=09 bool enable_wp, bool *mmap_changing); =20 /* mm helpers */ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *= vma, diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 4a06613525ee..cf1217e6f956 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -631,3 +631,57 @@ ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsig= ned long start, { =09return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing, 0); } + +int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, +=09=09=09unsigned long len, bool enable_wp, bool *mmap_changing) +{ +=09struct vm_area_struct *dst_vma; +=09pgprot_t newprot; +=09int err; + +=09/* +=09 * Sanitize the command parameters: +=09 */ +=09BUG_ON(start & ~PAGE_MASK); +=09BUG_ON(len & ~PAGE_MASK); + +=09/* Does the address range wrap, or is the span zero-sized? */ +=09BUG_ON(start + len <=3D start); + +=09down_read(&dst_mm->mmap_sem); + +=09/* +=09 * If memory mappings are changing because of non-cooperative +=09 * operation (e.g. mremap) running in parallel, bail out and +=09 * request the user to retry later +=09 */ +=09err =3D -EAGAIN; +=09if (mmap_changing && READ_ONCE(*mmap_changing)) +=09=09goto out_unlock; + +=09err =3D -ENOENT; +=09dst_vma =3D find_dst_vma(dst_mm, start, len); +=09/* +=09 * Make sure the vma is not shared, that the dst range is +=09 * both valid and fully within a single existing vma. +=09 */ +=09if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) +=09=09goto out_unlock; +=09if (!userfaultfd_wp(dst_vma)) +=09=09goto out_unlock; +=09if (!vma_is_anonymous(dst_vma)) +=09=09goto out_unlock; + +=09if (enable_wp) +=09=09newprot =3D vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE)); +=09else +=09=09newprot =3D vm_get_page_prot(dst_vma->vm_flags); + +=09change_protection(dst_vma, start, start + len, newprot, +=09=09=09 enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE); + +=09err =3D 0; +out_unlock: +=09up_read(&dst_mm->mmap_sem); +=09return err; +} --=20 2.24.1