From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932863AbaBUNX1 (ORCPT ); Fri, 21 Feb 2014 08:23:27 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:47616 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932986AbaBUNBv (ORCPT ); Fri, 21 Feb 2014 08:01:51 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Weijie Yang , Krzysztof Kozlowski , Andrew Morton , Linus Torvalds , Luis Henriques Subject: [PATCH 3.5 13/60] mm/swap: fix race on swap_info reuse between swapoff and swapon Date: Fri, 21 Feb 2014 13:00:40 +0000 Message-Id: <1392987687-15367-14-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.9.0 In-Reply-To: <1392987687-15367-1-git-send-email-luis.henriques@canonical.com> References: <1392987687-15367-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.5.7.31 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Weijie Yang commit f893ab41e4dae2fe8991faf5d86d029068d1ef3a upstream. swapoff clear swap_info's SWP_USED flag prematurely and free its resources after that. A concurrent swapon will reuse this swap_info while its previous resources are not cleared completely. These late freed resources are: - p->percpu_cluster - swap_cgroup_ctrl[type] - block_device setting - inode->i_flags &= ~S_SWAPFILE This patch clears the SWP_USED flag after all its resources are freed, so that swapon can reuse this swap_info by alloc_swap_info() safely. [akpm@linux-foundation.org: tidy up code comment] Signed-off-by: Weijie Yang Acked-by: Hugh Dickins Cc: Krzysztof Kozlowski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [ luis: backported to 3.5: adjusted context ] Signed-off-by: Luis Henriques --- mm/swapfile.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 71373d0..222928f 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1642,7 +1642,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) p->max = 0; swap_map = p->swap_map; p->swap_map = NULL; - p->flags = 0; frontswap_invalidate_area(type); spin_unlock(&swap_lock); mutex_unlock(&swapon_mutex); @@ -1662,6 +1661,16 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) mutex_unlock(&inode->i_mutex); } filp_close(swap_file, NULL); + + /* + * Clear the SWP_USED flag after all resources are freed so that swapon + * can reuse this swap_info in alloc_swap_info() safely. It is ok to + * not hold p->lock after we cleared its SWP_WRITEOK. + */ + spin_lock(&swap_lock); + p->flags = 0; + spin_unlock(&swap_lock); + err = 0; atomic_inc(&proc_poll_event); wake_up_interruptible(&proc_poll_wait); -- 1.9.0