From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F0BBC33CB3 for ; Thu, 16 Jan 2020 18:50:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21F88206B7 for ; Thu, 16 Jan 2020 18:50:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579200602; bh=yS4+U9L26l/jpK/Ofpa4jBRq/FVeVyV/IFoiS10BGNg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=yjeQJL6scQjwWSoI5Fp6Z+eBZrvnhbXCy7ueMdjJaNwuWxmdd8ln/Drjlak0RQAVA +PBWTQnfgQE7CnEElgl2YMsffyRZKorzdxMpzGNGccixNPkYicoxV6S4lltZbAby5o sPVDAAk8A8FD+LtqcXWbsVCn46G1ze3Cc8rzm6OI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436948AbgAPSuB (ORCPT ); Thu, 16 Jan 2020 13:50:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:44934 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389656AbgAPRJT (ORCPT ); Thu, 16 Jan 2020 12:09:19 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A2DEA22464; Thu, 16 Jan 2020 17:09:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579194558; bh=yS4+U9L26l/jpK/Ofpa4jBRq/FVeVyV/IFoiS10BGNg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Aqc39T2T5c5l7W/IMK+X5douBPqOUvCGycLHd4iKJNxHL5EYweLaP05zjmkxk+BkF /7TWkl0D1fIh7p+wPkfBOd5rP++7Rxk2Qy2nEkinQhnXLhOYvrssqEjZKwtQfhZSzN QTUoL1Ua0hRE8fzYBYBP4lRHHNA6vCHWHd36abss= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Andrea Arcangeli , Rik van Riel , Roman Gushchin , Michal Hocko , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH AUTOSEL 4.19 439/671] fork,memcg: alloc_thread_stack_node needs to set tsk->stack Date: Thu, 16 Jan 2020 12:01:17 -0500 Message-Id: <20200116170509.12787-176-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200116170509.12787-1-sashal@kernel.org> References: <20200116170509.12787-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrea Arcangeli [ Upstream commit 1bf4580e00a248a2c86269125390eb3648e1877c ] Commit 5eed6f1dff87 ("fork,memcg: fix crash in free_thread_stack on memcg charge fail") corrected two instances, but there was a third instance of this bug. Without setting tsk->stack, if memcg_charge_kernel_stack fails, it'll execute free_thread_stack() on a dangling pointer. Enterprise kernels are compiled with VMAP_STACK=y so this isn't critical, but custom VMAP_STACK=n builds should have some performance advantage, with the drawback of risking to fail fork because compaction didn't succeed. So as long as VMAP_STACK=n is a supported option it's worth fixing it upstream. Link: http://lkml.kernel.org/r/20190619011450.28048-1-aarcange@redhat.com Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") Signed-off-by: Andrea Arcangeli Reviewed-by: Rik van Riel Acked-by: Roman Gushchin Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- kernel/fork.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/fork.c b/kernel/fork.c index 1bd119530a49..1a2d18e98bf9 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -240,7 +240,11 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) struct page *page = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER); - return page ? page_address(page) : NULL; + if (likely(page)) { + tsk->stack = page_address(page); + return tsk->stack; + } + return NULL; #endif } -- 2.20.1