Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933439AbaBUNuQ (ORCPT ); Fri, 21 Feb 2014 08:50:16 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:46857 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932111AbaBUMt4 (ORCPT ); Fri, 21 Feb 2014 07:49:56 -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 3.11 034/121] mm/swap: fix race on swap_info reuse between swapoff and swapon Date: Fri, 21 Feb 2014 12:47:38 +0000 Message-Id: <1392986945-9693-35-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.9.0 In-Reply-To: <1392986945-9693-1-git-send-email-luis.henriques@canonical.com> References: <1392986945-9693-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.11.10.5 -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 3.11: 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 6cf2e60..d58fe88 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1675,7 +1675,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) p->max = 0; swap_map = p->swap_map; p->swap_map = NULL; - p->flags = 0; frontswap_map = frontswap_map_get(p); frontswap_map_set(p, NULL); spin_unlock(&p->lock); @@ -1698,6 +1697,16 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/