From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932530AbcCGWy3 (ORCPT ); Mon, 7 Mar 2016 17:54:29 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:38832 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932134AbcCGWwz (ORCPT ); Mon, 7 Mar 2016 17:52:55 -0500 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Matthew Wilcox , Hugh Dickins , Ohad Ben-Cohen , Konstantin Khlebnikov , Andrew Morton , Linus Torvalds , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 078/273] drivers/hwspinlock: fix race between radix tree insertion and lookup Date: Mon, 7 Mar 2016 14:47:49 -0800 Message-Id: <1457391064-6660-79-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.0 In-Reply-To: <1457391064-6660-1-git-send-email-kamal@canonical.com> References: <1457391064-6660-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Matthew Wilcox commit c6400ba7e13a41539342f1b6e1f9e78419cb0148 upstream. of_hwspin_lock_get_id() is protected by the RCU lock, which means that insertions can occur simultaneously with the lookup. If the radix tree transitions from a height of 0, we can see a slot with the indirect_ptr bit set, which will cause us to at least read random memory, and could cause other havoc. Fix this by using the newly introduced radix_tree_iter_retry(). Signed-off-by: Matthew Wilcox Cc: Hugh Dickins Cc: Ohad Ben-Cohen Cc: Konstantin Khlebnikov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Kamal Mostafa --- drivers/hwspinlock/hwspinlock_core.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c index 52f708b..d50c701 100644 --- a/drivers/hwspinlock/hwspinlock_core.c +++ b/drivers/hwspinlock/hwspinlock_core.c @@ -313,6 +313,10 @@ int of_hwspin_lock_get_id(struct device_node *np, int index) hwlock = radix_tree_deref_slot(slot); if (unlikely(!hwlock)) continue; + if (radix_tree_is_indirect_ptr(hwlock)) { + slot = radix_tree_iter_retry(&iter); + continue; + } if (hwlock->bank->dev->of_node == args.np) { ret = 0; -- 2.7.0