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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 19424C2D0DB for ; Fri, 24 Jan 2020 11:25:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E1015206D4 for ; Fri, 24 Jan 2020 11:25:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579865107; bh=e/Q65EoOC/T9/Yf5HKWoSq1rPBPyrAcJUgEkmtb5s5M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=EPIAWXUFjEq3FHQ8FjQSv91ucX3sgDMEnuJb0ePJs5YYTlJ3ICmkEx0OuIAWy2DJb YINllPUbC2hmSKo3fbWueXJk3fhMVqn9HZCrqh8pTFbR4CKn/uUbXahQ4Th/rd5W+C eS040Q/UB9X5fNOcYZAPn/a+FgIUL0BMqMkDmJ00= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391142AbgAXLZG (ORCPT ); Fri, 24 Jan 2020 06:25:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:38906 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2403836AbgAXLZD (ORCPT ); Fri, 24 Jan 2020 06:25:03 -0500 Received: from localhost (ip-213-127-102-57.ip.prioritytelecom.net [213.127.102.57]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 64F6E206D4; Fri, 24 Jan 2020 11:25:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579865102; bh=e/Q65EoOC/T9/Yf5HKWoSq1rPBPyrAcJUgEkmtb5s5M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NSiYHlIqp+c+fU1zADKD7lVwi5oZIjc3uWz+excug3FD+PS3nAhmSZMtOe4dEXz49 4M4tV3aR4gNaIJw0gYtYGLLRtdhiDzbmvE8kiLbLgNjhcNSS5c7ilpHx2bHcP+13pH g4tXTkwv1syYBDUMArJDAr8x51s52nkM60hE9Grk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andrea Arcangeli , Rik van Riel , Roman Gushchin , Michal Hocko , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.19 454/639] fork,memcg: alloc_thread_stack_node needs to set tsk->stack Date: Fri, 24 Jan 2020 10:30:24 +0100 Message-Id: <20200124093144.002461222@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200124093047.008739095@linuxfoundation.org> References: <20200124093047.008739095@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 1bd119530a492..1a2d18e98bf99 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