From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:44038 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1164386AbeE1Kz1 (ORCPT ); Mon, 28 May 2018 06:55:27 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vinayak Menon , Catalin Marinas , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.14 311/496] mm/kmemleak.c: wait for scan completion before disabling free Date: Mon, 28 May 2018 12:01:36 +0200 Message-Id: <20180528100332.924396565@linuxfoundation.org> In-Reply-To: <20180528100319.498712256@linuxfoundation.org> References: <20180528100319.498712256@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vinayak Menon [ Upstream commit 914b6dfff790544d9b77dfd1723adb3745ec9700 ] A crash is observed when kmemleak_scan accesses the object->pointer, likely due to the following race. TASK A TASK B TASK C kmemleak_write (with "scan" and NOT "scan=on") kmemleak_scan() create_object kmem_cache_alloc fails kmemleak_disable kmemleak_do_cleanup kmemleak_free_enabled = 0 kfree kmemleak_free bails out (kmemleak_free_enabled is 0) slub frees object->pointer update_checksum crash - object->pointer freed (DEBUG_PAGEALLOC) kmemleak_do_cleanup waits for the scan thread to complete, but not for direct call to kmemleak_scan via kmemleak_write. So add a wait for kmemleak_scan completion before disabling kmemleak_free, and while at it fix the comment on stop_scan_thread. [vinmenon@codeaurora.org: fix stop_scan_thread comment] Link: http://lkml.kernel.org/r/1522219972-22809-1-git-send-email-vinmenon@codeaurora.org Link: http://lkml.kernel.org/r/1522063429-18992-1-git-send-email-vinmenon@codeaurora.org Signed-off-by: Vinayak Menon Reviewed-by: Catalin Marinas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- mm/kmemleak.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -1658,8 +1658,7 @@ static void start_scan_thread(void) } /* - * Stop the automatic memory scanning thread. This function must be called - * with the scan_mutex held. + * Stop the automatic memory scanning thread. */ static void stop_scan_thread(void) { @@ -1922,12 +1921,15 @@ static void kmemleak_do_cleanup(struct w { stop_scan_thread(); + mutex_lock(&scan_mutex); /* - * Once the scan thread has stopped, it is safe to no longer track - * object freeing. Ordering of the scan thread stopping and the memory - * accesses below is guaranteed by the kthread_stop() function. + * Once it is made sure that kmemleak_scan has stopped, it is safe to no + * longer track object freeing. Ordering of the scan thread stopping and + * the memory accesses below is guaranteed by the kthread_stop() + * function. */ kmemleak_free_enabled = 0; + mutex_unlock(&scan_mutex); if (!kmemleak_found_leaks) __kmemleak_do_cleanup();