Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753212AbdLDQb5 (ORCPT ); Mon, 4 Dec 2017 11:31:57 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:33366 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751736AbdLDQCi (ORCPT ); Mon, 4 Dec 2017 11:02:38 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mike Kravetz , Vlastimil Babka , Michal Hocko , Johannes Weiner , Joonsoo Kim , Michal Nazarewicz , Laura Abbott , Mel Gorman , Andrew Morton , Linus Torvalds Subject: [PATCH 4.9 04/38] mm/cma: fix alloc_contig_range ret code/potential leak Date: Mon, 4 Dec 2017 16:59:44 +0100 Message-Id: <20171204160007.625016030@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171204160007.448534903@linuxfoundation.org> References: <20171204160007.448534903@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2583 Lines: 63 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mike Kravetz commit 63cd448908b5eb51d84c52f02b31b9b4ccd1cb5a upstream. If the call __alloc_contig_migrate_range() in alloc_contig_range returns -EBUSY, processing continues so that test_pages_isolated() is called where there is a tracepoint to identify the busy pages. However, it is possible for busy pages to become available between the calls to these two routines. In this case, the range of pages may be allocated. Unfortunately, the original return code (ret == -EBUSY) is still set and returned to the caller. Therefore, the caller believes the pages were not allocated and they are leaked. Update the comment to indicate that allocation is still possible even if __alloc_contig_migrate_range returns -EBUSY. Also, clear return code in this case so that it is not accidentally used or returned to caller. Link: http://lkml.kernel.org/r/20171122185214.25285-1-mike.kravetz@oracle.com Fixes: 8ef5849fa8a2 ("mm/cma: always check which page caused allocation failure") Signed-off-by: Mike Kravetz Acked-by: Vlastimil Babka Acked-by: Michal Hocko Acked-by: Johannes Weiner Acked-by: Joonsoo Kim Cc: Michal Nazarewicz Cc: Laura Abbott Cc: Michal Hocko Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/page_alloc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7309,11 +7309,18 @@ int alloc_contig_range(unsigned long sta /* * In case of -EBUSY, we'd like to know which page causes problem. - * So, just fall through. We will check it in test_pages_isolated(). + * So, just fall through. test_pages_isolated() has a tracepoint + * which will report the busy page. + * + * It is possible that busy pages could become available before + * the call to test_pages_isolated, and the range will actually be + * allocated. So, if we fall through be sure to clear ret so that + * -EBUSY is not accidentally used or returned to caller. */ ret = __alloc_contig_migrate_range(&cc, start, end); if (ret && ret != -EBUSY) goto done; + ret =0; /* * Pages from [start, end) are within a MAX_ORDER_NR_PAGES