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=-6.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 18EF7C43381 for ; Tue, 26 Mar 2019 06:40:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC2492087E for ; Tue, 26 Mar 2019 06:40:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553582419; bh=qbCNYG0yrTYp+Su9oqJA0njdbBO+vn4rkxzFTHmHmYk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fVagbbtVB8vZ7f6CBxcZH6soN2wYi0zfcPph4ByZlgxtgH1vh9VfFHFzZ9i0vMpUi wjLq+07JebfclTd08+3jKeVllWsvBz80gOz5k04Bp7oAq2uFH5jBKX/uMpkLojhmPe JFm3OLzNrM44n6rUYXbNeGnMNOLwXHcc6lsH0cmw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732526AbfCZGkS (ORCPT ); Tue, 26 Mar 2019 02:40:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:56490 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732360AbfCZGkQ (ORCPT ); Tue, 26 Mar 2019 02:40:16 -0400 Received: from localhost (unknown [104.132.152.111]) (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 7769E2086C; Tue, 26 Mar 2019 06:40:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553582415; bh=qbCNYG0yrTYp+Su9oqJA0njdbBO+vn4rkxzFTHmHmYk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1mHw5slY/rFIsrWnfWiP0xGqnbD2bl9xHh+mShHlHOpN5blMzZH1DeIPAutqGsDQk b0g7StwS5AbOfdyDKC/iabiVvmhyAtVpt6ON/4DJr5VZCNYZHVOH9olJl4U+ERw8FA eONDLc43mf35shWmVPSdOObr8Zo9YMtLfzXoWJQU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Thomas Gleixner , Josh Poimboeuf , Borislav Petkov , Andrew Morton , syzbot , "H. Peter Anvin" , Masahiro Yamada , Michal Marek , linux-kbuild@vger.kernel.org Subject: [PATCH 5.0 48/52] x86/unwind: Add hardcoded ORC entry for NULL Date: Tue, 26 Mar 2019 15:30:35 +0900 Message-Id: <20190326042703.541084024@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190326042700.963224437@linuxfoundation.org> References: <20190326042700.963224437@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore 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 5.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit ac5ceccce5501e43d217c596e4ee859f2a3fef79 upstream. When the ORC unwinder is invoked for an oops caused by IP==0, it currently has no idea what to do because there is no debug information for the stack frame of NULL. But if RIP is NULL, it is very likely that the last successfully executed instruction was an indirect CALL/JMP, and it is possible to unwind out in the same way as for the first instruction of a normal function. Hardcode a corresponding ORC entry. With an artificially-added NULL call in prctl_set_seccomp(), before this patch, the trace is: Call Trace: ? __x64_sys_prctl+0x402/0x680 ? __ia32_sys_prctl+0x6e0/0x6e0 ? __do_page_fault+0x457/0x620 ? do_syscall_64+0x6d/0x160 ? entry_SYSCALL_64_after_hwframe+0x44/0xa9 After this patch, the trace looks like this: Call Trace: __x64_sys_prctl+0x402/0x680 ? __ia32_sys_prctl+0x6e0/0x6e0 ? __do_page_fault+0x457/0x620 do_syscall_64+0x6d/0x160 entry_SYSCALL_64_after_hwframe+0x44/0xa9 prctl_set_seccomp() still doesn't show up in the trace because for some reason, tail call optimization is only disabled in builds that use the frame pointer unwinder. Signed-off-by: Jann Horn Signed-off-by: Thomas Gleixner Acked-by: Josh Poimboeuf Cc: Borislav Petkov Cc: Andrew Morton Cc: syzbot Cc: "H. Peter Anvin" Cc: Masahiro Yamada Cc: Michal Marek Cc: linux-kbuild@vger.kernel.org Link: https://lkml.kernel.org/r/20190301031201.7416-2-jannh@google.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/unwind_orc.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) --- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -113,6 +113,20 @@ static struct orc_entry *orc_ftrace_find } #endif +/* + * If we crash with IP==0, the last successfully executed instruction + * was probably an indirect function call with a NULL function pointer, + * and we don't have unwind information for NULL. + * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function + * pointer into its parent and then continue normally from there. + */ +static struct orc_entry null_orc_entry = { + .sp_offset = sizeof(long), + .sp_reg = ORC_REG_SP, + .bp_reg = ORC_REG_UNDEFINED, + .type = ORC_TYPE_CALL +}; + static struct orc_entry *orc_find(unsigned long ip) { static struct orc_entry *orc; @@ -120,6 +134,9 @@ static struct orc_entry *orc_find(unsign if (!orc_init) return NULL; + if (ip == 0) + return &null_orc_entry; + /* For non-init vmlinux addresses, use the fast lookup table: */ if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) { unsigned int idx, start, stop;