From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755438AbbCaQ7b (ORCPT ); Tue, 31 Mar 2015 12:59:31 -0400 Received: from p3plsmtps2ded04.prod.phx3.secureserver.net ([208.109.80.198]:40110 "EHLO p3plsmtps2ded04.prod.phx3.secureserver.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752623AbbCaQ72 (ORCPT ); Tue, 31 Mar 2015 12:59:28 -0400 x-originating-ip: 72.167.245.219 From: "K. Y. Srinivasan" To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, devel@linuxdriverproject.org, olaf@aepfle.de, apw@canonical.com, vkuznets@redhat.com, jasowang@redhat.com Cc: "K. Y. Srinivasan" Subject: [PATCH 1/2] Drivers: hv: hv_balloon: correctly handle val.freeram X-Mailer: git-send-email 1.7.4.1 In-Reply-To: <1427825783-6549-1-git-send-email-kys@microsoft.com> References: <1427825783-6549-1-git-send-email-kys@microsoft.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vitaly Kuznetsov 'Drivers: hv: hv_balloon: refuse to balloon below the floor' fix does not correctly handle the case when val.freeram < num_pages as val.freeram is __kernel_ulong_t and the 'val.freeram - num_pages' value will be a huge positive value instead of being negative. Usually host doesn't ask us to balloon more than val.freeram but in case he have a memory hog started after we post the last pressure report we can get into troubles. Suggested-by: Laszlo Ersek Signed-off-by: Vitaly Kuznetsov Reviewed-by: Laszlo Ersek Signed-off-by: K. Y. Srinivasan --- drivers/hv/hv_balloon.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c index 74312c8..4052ad8 100644 --- a/drivers/hv/hv_balloon.c +++ b/drivers/hv/hv_balloon.c @@ -1155,7 +1155,7 @@ static void balloon_up(struct work_struct *dummy) floor = compute_balloon_floor(); /* Refuse to balloon below the floor, keep the 2M granularity. */ - if (val.freeram - num_pages < floor) { + if (val.freeram < num_pages || val.freeram - num_pages < floor) { num_pages = val.freeram > floor ? (val.freeram - floor) : 0; num_pages -= num_pages % PAGES_IN_2M; } -- 1.7.4.1