From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S940229AbeE1Qfy (ORCPT ); Mon, 28 May 2018 12:35:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:56586 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934707AbeE1KIa (ORCPT ); Mon, 28 May 2018 06:08:30 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ross Lagerwall , Boris Ostrovsky , Juergen Gross , Sasha Levin Subject: [PATCH 3.18 038/185] xen/grant-table: Use put_page instead of free_page Date: Mon, 28 May 2018 12:01:19 +0200 Message-Id: <20180528100053.826648641@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180528100050.700971285@linuxfoundation.org> References: <20180528100050.700971285@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review 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 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ross Lagerwall [ Upstream commit 3ac7292a25db1c607a50752055a18aba32ac2176 ] The page given to gnttab_end_foreign_access() to free could be a compound page so use put_page() instead of free_page() since it can handle both compound and single pages correctly. This bug was discovered when migrating a Xen VM with several VIFs and CONFIG_DEBUG_VM enabled. It hits a BUG usually after fewer than 10 iterations. All netfront devices disconnect from the backend during a suspend/resume and this will call gnttab_end_foreign_access() if a netfront queue has an outstanding skb. The mismatch between calling get_page() and free_page() on a compound page causes a reference counting error which is detected when DEBUG_VM is enabled. Signed-off-by: Ross Lagerwall Reviewed-by: Boris Ostrovsky Signed-off-by: Juergen Gross Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/xen/grant-table.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -322,7 +322,7 @@ static void gnttab_handle_deferred(unsig if (entry->page) { pr_debug("freeing g.e. %#x (pfn %#lx)\n", entry->ref, page_to_pfn(entry->page)); - __free_page(entry->page); + put_page(entry->page); } else pr_info("freeing g.e. %#x\n", entry->ref); kfree(entry); @@ -378,7 +378,7 @@ void gnttab_end_foreign_access(grant_ref if (gnttab_end_foreign_access_ref(ref, readonly)) { put_free_entry(ref); if (page != 0) - free_page(page); + put_page(virt_to_page(page)); } else gnttab_add_deferred(ref, readonly, page ? virt_to_page(page) : NULL);