From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 191FD6B0263 for ; Wed, 12 Oct 2016 06:41:22 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id 190so38731246pfv.0 for ; Wed, 12 Oct 2016 03:41:22 -0700 (PDT) Received: from mail-pf0-f196.google.com (mail-pf0-f196.google.com. [209.85.192.196]) by mx.google.com with ESMTPS id c14si8687441pfc.93.2016.10.12.03.41.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 12 Oct 2016 03:41:21 -0700 (PDT) Received: by mail-pf0-f196.google.com with SMTP id s8so2479768pfj.2 for ; Wed, 12 Oct 2016 03:41:21 -0700 (PDT) Date: Wed, 12 Oct 2016 12:41:18 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: kmemleak: Ensure that the task stack is not freed during scanning Message-ID: <20161012104118.GC9523@dhcp22.suse.cz> References: <1476266223-14325-1-git-send-email-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1476266223-14325-1-git-send-email-catalin.marinas@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Catalin Marinas Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , CAI Qian On Wed 12-10-16 10:57:03, Catalin Marinas wrote: > 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. Looks good to me > 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 Acked-by: Michal Hocko > --- > > 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 -- Michal Hocko SUSE Labs -- 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