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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 25 Feb 2019 20:52:41 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x1PKqeR561276406 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 25 Feb 2019 20:52:40 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2EBB2A4040; Mon, 25 Feb 2019 20:52:40 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 12FBCA4051; Mon, 25 Feb 2019 20:52:37 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.204.243]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 25 Feb 2019 20:52:36 +0000 (GMT) Date: Mon, 25 Feb 2019 22:52:34 +0200 From: Mike Rapoport To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Hugh Dickins , Maya Gokhale , Jerome Glisse , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Shaohua Li , Marty McFadden , Andrea Arcangeli , Mike Kravetz , Denis Plotnikov , Mike Rapoport , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" , Rik van Riel Subject: Re: [PATCH v2 20/26] userfaultfd: wp: support write protection for userfault vma range References: <20190212025632.28946-1-peterx@redhat.com> <20190212025632.28946-21-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190212025632.28946-21-peterx@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19022520-0008-0000-0000-000002C4CB5D X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022520-0009-0000-0000-00002231122F Message-Id: <20190225205233.GC10454@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-25_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902250149 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: On Tue, Feb 12, 2019 at 10:56:26AM +0800, Peter Xu wrote: > 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] > 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 765ce884cec0..8f6e6ed544fb 100644 > --- a/include/linux/userfaultfd_k.h > +++ b/include/linux/userfaultfd_k.h > @@ -39,6 +39,9 @@ extern ssize_t mfill_zeropage(struct mm_struct *dst_mm, > unsigned long dst_start, > unsigned long len, > bool *mmap_changing); > +extern int mwriteprotect_range(struct mm_struct *dst_mm, > + unsigned long start, unsigned long len, > + bool enable_wp, bool *mmap_changing); > > /* 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 fefa81c301b7..529d180bb4d7 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -639,3 +639,57 @@ ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, > { > return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing, 0); > } > + > +int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, > + unsigned long len, bool enable_wp, bool *mmap_changing) > +{ > + struct vm_area_struct *dst_vma; > + pgprot_t newprot; > + int err; > + > + /* > + * Sanitize the command parameters: > + */ > + BUG_ON(start & ~PAGE_MASK); > + BUG_ON(len & ~PAGE_MASK); > + > + /* Does the address range wrap, or is the span zero-sized? */ > + BUG_ON(start + len <= start); I'd replace these BUG_ON()s with if (WARN_ON()) return -EINVAL; > + > + down_read(&dst_mm->mmap_sem); > + > + /* > + * If memory mappings are changing because of non-cooperative > + * operation (e.g. mremap) running in parallel, bail out and > + * request the user to retry later > + */ > + err = -EAGAIN; > + if (mmap_changing && READ_ONCE(*mmap_changing)) > + goto out_unlock; > + > + err = -ENOENT; > + dst_vma = vma_find_uffd(dst_mm, start, len); > + /* > + * Make sure the vma is not shared, that the dst range is > + * both valid and fully within a single existing vma. > + */ > + if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) > + goto out_unlock; > + if (!userfaultfd_wp(dst_vma)) > + goto out_unlock; > + if (!vma_is_anonymous(dst_vma)) > + goto out_unlock; > + > + if (enable_wp) > + newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE)); > + else > + newprot = vm_get_page_prot(dst_vma->vm_flags); > + > + change_protection(dst_vma, start, start + len, newprot, > + enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE); > + > + err = 0; > +out_unlock: > + up_read(&dst_mm->mmap_sem); > + return err; > +} > -- > 2.17.1 > -- Sincerely yours, Mike.