From mboxrd@z Thu Jan 1 00:00:00 1970 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6DFF0C433EF for ; Fri, 29 Apr 2022 10:44:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344899AbiD2Kri (ORCPT ); Fri, 29 Apr 2022 06:47:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357957AbiD2Kqv (ORCPT ); Fri, 29 Apr 2022 06:46:51 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4C97BC8BFA; Fri, 29 Apr 2022 03:42:55 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D87A0B83451; Fri, 29 Apr 2022 10:42:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 508B5C385A4; Fri, 29 Apr 2022 10:42:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651228972; bh=JBM7TEKp7jX5Ll6RGCQ6sUtSgSG6dnk4IbVRKCZ0Qv4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ql9jM7WD/JEaDF7bej61KXAgT7us5p8Xrms0i+AgUdTQo0Ob0hd1xwQqy9cM/335g zIGfnoIaon/OHb4t2IAe+XHUrQgb/R2ofe4NZgguoIuk31fw8rN1tmm4gsvRxTrWCc D8npdVSoPUQWWNNcMgJh6iX1TU+hY3lwCOViW0EU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Andreas Gruenbacher , Anand Jain Subject: [PATCH 5.15 17/33] iov_iter: Introduce fault_in_iov_iter_writeable Date: Fri, 29 Apr 2022 12:42:04 +0200 Message-Id: <20220429104052.840367250@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220429104052.345760505@linuxfoundation.org> References: <20220429104052.345760505@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andreas Gruenbacher commit cdd591fc86e38ad3899196066219fbbd845f3162 upstream Introduce a new fault_in_iov_iter_writeable helper for safely faulting in an iterator for writing. Uses get_user_pages() to fault in the pages without actually writing to them, which would be destructive. We'll use fault_in_iov_iter_writeable in gfs2 once we've determined that the iterator passed to .read_iter isn't in memory. Signed-off-by: Andreas Gruenbacher Signed-off-by: Anand Jain Signed-off-by: Greg Kroah-Hartman --- include/linux/pagemap.h | 1 include/linux/uio.h | 1 lib/iov_iter.c | 39 +++++++++++++++++++++++++++++ mm/gup.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 104 insertions(+) --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -736,6 +736,7 @@ extern void add_page_wait_queue(struct p * Fault in userspace address range. */ size_t fault_in_writeable(char __user *uaddr, size_t size); +size_t fault_in_safe_writeable(const char __user *uaddr, size_t size); size_t fault_in_readable(const char __user *uaddr, size_t size); int add_to_page_cache_locked(struct page *page, struct address_space *mapping, --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -134,6 +134,7 @@ size_t copy_page_from_iter_atomic(struct void iov_iter_advance(struct iov_iter *i, size_t bytes); void iov_iter_revert(struct iov_iter *i, size_t bytes); size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t bytes); +size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t bytes); size_t iov_iter_single_seg_count(const struct iov_iter *i); size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, struct iov_iter *i); --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -468,6 +468,45 @@ size_t fault_in_iov_iter_readable(const } EXPORT_SYMBOL(fault_in_iov_iter_readable); +/* + * fault_in_iov_iter_writeable - fault in iov iterator for writing + * @i: iterator + * @size: maximum length + * + * Faults in the iterator using get_user_pages(), i.e., without triggering + * hardware page faults. This is primarily useful when we already know that + * some or all of the pages in @i aren't in memory. + * + * Returns the number of bytes not faulted in, like copy_to_user() and + * copy_from_user(). + * + * Always returns 0 for non-user-space iterators. + */ +size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size) +{ + if (iter_is_iovec(i)) { + size_t count = min(size, iov_iter_count(i)); + const struct iovec *p; + size_t skip; + + size -= count; + for (p = i->iov, skip = i->iov_offset; count; p++, skip = 0) { + size_t len = min(count, p->iov_len - skip); + size_t ret; + + if (unlikely(!len)) + continue; + ret = fault_in_safe_writeable(p->iov_base + skip, len); + count -= len - ret; + if (ret) + break; + } + return count + size; + } + return 0; +} +EXPORT_SYMBOL(fault_in_iov_iter_writeable); + void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov, unsigned long nr_segs, size_t count) --- a/mm/gup.c +++ b/mm/gup.c @@ -1716,6 +1716,69 @@ out: } EXPORT_SYMBOL(fault_in_writeable); +/* + * fault_in_safe_writeable - fault in an address range for writing + * @uaddr: start of address range + * @size: length of address range + * + * Faults in an address range using get_user_pages, i.e., without triggering + * hardware page faults. This is primarily useful when we already know that + * some or all of the pages in the address range aren't in memory. + * + * Other than fault_in_writeable(), this function is non-destructive. + * + * Note that we don't pin or otherwise hold the pages referenced that we fault + * in. There's no guarantee that they'll stay in memory for any duration of + * time. + * + * Returns the number of bytes not faulted in, like copy_to_user() and + * copy_from_user(). + */ +size_t fault_in_safe_writeable(const char __user *uaddr, size_t size) +{ + unsigned long start = (unsigned long)untagged_addr(uaddr); + unsigned long end, nstart, nend; + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma = NULL; + int locked = 0; + + nstart = start & PAGE_MASK; + end = PAGE_ALIGN(start + size); + if (end < nstart) + end = 0; + for (; nstart != end; nstart = nend) { + unsigned long nr_pages; + long ret; + + if (!locked) { + locked = 1; + mmap_read_lock(mm); + vma = find_vma(mm, nstart); + } else if (nstart >= vma->vm_end) + vma = vma->vm_next; + if (!vma || vma->vm_start >= end) + break; + nend = end ? min(end, vma->vm_end) : vma->vm_end; + if (vma->vm_flags & (VM_IO | VM_PFNMAP)) + continue; + if (nstart < vma->vm_start) + nstart = vma->vm_start; + nr_pages = (nend - nstart) / PAGE_SIZE; + ret = __get_user_pages_locked(mm, nstart, nr_pages, + NULL, NULL, &locked, + FOLL_TOUCH | FOLL_WRITE); + if (ret <= 0) + break; + nend = nstart + ret * PAGE_SIZE; + } + if (locked) + mmap_read_unlock(mm); + if (nstart == end) + return 0; + return size - min_t(size_t, nstart - start, size); +} +EXPORT_SYMBOL(fault_in_safe_writeable); + /** * fault_in_readable - fault in userspace address range for reading * @uaddr: start of user address range