From patchwork Mon Jun 13 10:10:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 12879589 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 CED55CCA47B for ; Mon, 13 Jun 2022 13:57:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380118AbiFMN5g (ORCPT ); Mon, 13 Jun 2022 09:57:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380287AbiFMNyB (ORCPT ); Mon, 13 Jun 2022 09:54:01 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03A4D42A21; Mon, 13 Jun 2022 04:34:26 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 91BBF612D0; Mon, 13 Jun 2022 11:34:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DE7FC34114; Mon, 13 Jun 2022 11:34:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655120065; bh=ZjDVsKHFBSnws36ePAnZg275uQcp5H4PcRvFzlD2OCY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GdOw7yAMTFxOtA1uIG2rgNiapakQfWnLMWiyHKauhP60cOEWFLhhU6YCfuehZ7/3F SEMXPUP2zht6b6B9NZ5JUOBkLujbvj8izhd3/QNwn8xvHfP6o+PN9XsSrQZDUAe3tu G+4cVlx+UfapznwBQ8Vo+Zp5V5G4MeRrM+yCMJTE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jeff Layton , David Howells , Alexander Viro , Dominique Martinet , Mike Marshall , Gao Xiang , linux-afs@lists.infradead.org, v9fs-developer@lists.sourceforge.net, devel@lists.orangefs.org, linux-erofs@lists.ozlabs.org, linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org, Sasha Levin Subject: [PATCH 5.18 222/339] iov_iter: Fix iter_xarray_get_pages{,_alloc}() Date: Mon, 13 Jun 2022 12:10:47 +0200 Message-Id: <20220613094933.390057932@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094926.497929857@linuxfoundation.org> References: <20220613094926.497929857@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: David Howells [ Upstream commit 6c77676645ad42993e0a8bdb8dafa517851a352a ] The maths at the end of iter_xarray_get_pages() to calculate the actual size doesn't work under some circumstances, such as when it's been asked to extract a partial single page. Various terms of the equation cancel out and you end up with actual == offset. The same issue exists in iter_xarray_get_pages_alloc(). Fix these to just use min() to select the lesser amount from between the amount of page content transcribed into the buffer, minus the offset, and the size limit specified. This doesn't appear to have caused a problem yet upstream because network filesystems aren't getting the pages from an xarray iterator, but rather passing it directly to the socket, which just iterates over it. Cachefiles *does* do DIO from one to/from ext4/xfs/btrfs/etc. but it always asks for whole pages to be written or read. Fixes: 7ff5062079ef ("iov_iter: Add ITER_XARRAY") Reported-by: Jeff Layton Signed-off-by: David Howells cc: Alexander Viro cc: Dominique Martinet cc: Mike Marshall cc: Gao Xiang cc: linux-afs@lists.infradead.org cc: v9fs-developer@lists.sourceforge.net cc: devel@lists.orangefs.org cc: linux-erofs@lists.ozlabs.org cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org Signed-off-by: Al Viro Signed-off-by: Sasha Levin --- lib/iov_iter.c | 20 ++++---------------- 1 file changed, 4 insertions(+), 16 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 6dd5330f7a99..dda6d5f481c1 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1434,7 +1434,7 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i, { unsigned nr, offset; pgoff_t index, count; - size_t size = maxsize, actual; + size_t size = maxsize; loff_t pos; if (!size || !maxpages) @@ -1461,13 +1461,7 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i, if (nr == 0) return 0; - actual = PAGE_SIZE * nr; - actual -= offset; - if (nr == count && size > 0) { - unsigned last_offset = (nr > 1) ? 0 : offset; - actual -= PAGE_SIZE - (last_offset + size); - } - return actual; + return min(nr * PAGE_SIZE - offset, maxsize); } /* must be done on non-empty ITER_IOVEC one */ @@ -1602,7 +1596,7 @@ static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i, struct page **p; unsigned nr, offset; pgoff_t index, count; - size_t size = maxsize, actual; + size_t size = maxsize; loff_t pos; if (!size) @@ -1631,13 +1625,7 @@ static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i, if (nr == 0) return 0; - actual = PAGE_SIZE * nr; - actual -= offset; - if (nr == count && size > 0) { - unsigned last_offset = (nr > 1) ? 0 : offset; - actual -= PAGE_SIZE - (last_offset + size); - } - return actual; + return min(nr * PAGE_SIZE - offset, maxsize); } ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,