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=-13.1 required=3.0 tests=BAYES_00,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 C31E0C43446 for ; Mon, 27 Jul 2020 23:24:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87F092173E for ; Mon, 27 Jul 2020 23:24:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595892263; bh=k9WgX49UhER9eYl15sr7XTWMTSzUTaFe3tk7B9RNLmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=MS4qefQl2paQYelAcJTfldO4GOAZydsavRLu66EddWf/9EVri6Dj6YaKF7aX1u5Sd 8gaAbUSu5Bfnau9MVFDLOGeE6UOFyKMYjQCh06e77SM9l5m2Adi1OCDsJGW3YViH4t bCNcL7ADF8+ImgQOWL3kHZtqJKQq3Q2/U/Jrad64= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728177AbgG0XYW (ORCPT ); Mon, 27 Jul 2020 19:24:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:35114 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728100AbgG0XYM (ORCPT ); Mon, 27 Jul 2020 19:24:12 -0400 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 3867D21883; Mon, 27 Jul 2020 23:24:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595892251; bh=k9WgX49UhER9eYl15sr7XTWMTSzUTaFe3tk7B9RNLmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KVoC36gWoyUVaYlGlu9SYw3GfgoS0fGGziugZ68YoqV66eGEEzdFZsgCVjIC0qejB p/TgvgxQX2B0xb1KODFw600ziFPDS1I9tK2pg3RBfrlFs6AnFk3ZBwlkvB9fm/1sXX bJMjska1JzVw6nSmwVH5elveDufR4ktI01/PhaXQ= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Josh Poimboeuf , Wang ShaoBo , Thomas Gleixner , Sasha Levin Subject: [PATCH AUTOSEL 5.7 19/25] x86/stacktrace: Fix reliable check for empty user task stacks Date: Mon, 27 Jul 2020 19:23:39 -0400 Message-Id: <20200727232345.717432-19-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200727232345.717432-1-sashal@kernel.org> References: <20200727232345.717432-1-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: Josh Poimboeuf [ Upstream commit 039a7a30ec102ec866d382a66f87f6f7654f8140 ] If a user task's stack is empty, or if it only has user regs, ORC reports it as a reliable empty stack. But arch_stack_walk_reliable() incorrectly treats it as unreliable. That happens because the only success path for user tasks is inside the loop, which only iterates on non-empty stacks. Generally, a user task must end in a user regs frame, but an empty stack is an exception to that rule. Thanks to commit 71c95825289f ("x86/unwind/orc: Fix error handling in __unwind_start()"), unwind_start() now sets state->error appropriately. So now for both ORC and FP unwinders, unwind_done() and !unwind_error() always means the end of the stack was successfully reached. So the success path for kthreads is no longer needed -- it can also be used for empty user tasks. Reported-by: Wang ShaoBo Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Tested-by: Wang ShaoBo Link: https://lkml.kernel.org/r/f136a4e5f019219cbc4f4da33b30c2f44fa65b84.1594994374.git.jpoimboe@redhat.com Signed-off-by: Sasha Levin --- arch/x86/kernel/stacktrace.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c index 6ad43fc44556e..2fd698e28e4d5 100644 --- a/arch/x86/kernel/stacktrace.c +++ b/arch/x86/kernel/stacktrace.c @@ -58,7 +58,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, * or a page fault), which can make frame pointers * unreliable. */ - if (IS_ENABLED(CONFIG_FRAME_POINTER)) return -EINVAL; } @@ -81,10 +80,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, if (unwind_error(&state)) return -EINVAL; - /* Success path for non-user tasks, i.e. kthreads and idle tasks */ - if (!(task->flags & (PF_KTHREAD | PF_IDLE))) - return -EINVAL; - return 0; } -- 2.25.1