From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f72.google.com (mail-pa0-f72.google.com [209.85.220.72]) by kanga.kvack.org (Postfix) with ESMTP id 570C66B0069 for ; Wed, 12 Oct 2016 05:57:11 -0400 (EDT) Received: by mail-pa0-f72.google.com with SMTP id hm5so38895063pac.4 for ; Wed, 12 Oct 2016 02:57:11 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id d62si5065026pga.215.2016.10.12.02.57.10 for ; Wed, 12 Oct 2016 02:57:10 -0700 (PDT) From: Catalin Marinas Subject: [PATCH] mm: kmemleak: Ensure that the task stack is not freed during scanning Date: Wed, 12 Oct 2016 10:57:03 +0100 Message-Id: <1476266223-14325-1-git-send-email-catalin.marinas@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , CAI Qian Commit 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") may cause the task->stack to be freed during kmemleak_scan() execution, leading to either a NULL pointer fault (if task->stack is NULL) or kmemleak accessing already freed memory. This patch uses the new try_get_task_stack() API to ensure that the task stack is not freed during kmemleak stack scanning. Fixes: 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") Cc: Andrew Morton Cc: Andy Lutomirski Cc: CAI Qian Reported-by: CAI Qian Signed-off-by: Catalin Marinas --- This was reported in a subsequent comment here: https://bugzilla.kernel.org/show_bug.cgi?id=173901 However, the original bugzilla entry doesn't look related to task stack freeing as it was first reported on 4.8-rc8. Andy, sorry for cc'ing you to bugzilla, please feel free to remove your email from the bug above (I can't seem to be able to do it). mm/kmemleak.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index a5e453cf05c4..e5355a5b423f 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -1453,8 +1453,11 @@ static void kmemleak_scan(void) read_lock(&tasklist_lock); do_each_thread(g, p) { - scan_block(task_stack_page(p), task_stack_page(p) + - THREAD_SIZE, NULL); + void *stack = try_get_task_stack(p); + if (stack) { + scan_block(stack, stack + THREAD_SIZE, NULL); + put_task_stack(p); + } } while_each_thread(g, p); read_unlock(&tasklist_lock); } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org