From patchwork Thu Feb 11 15:02:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 381775 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=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, 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 3350CC433E0 for ; Thu, 11 Feb 2021 15:16:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B21564EEA for ; Thu, 11 Feb 2021 15:16:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229701AbhBKPO4 (ORCPT ); Thu, 11 Feb 2021 10:14:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:51400 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229960AbhBKPKA (ORCPT ); Thu, 11 Feb 2021 10:10:00 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id EA0E664EBB; Thu, 11 Feb 2021 15:03:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1613055815; bh=xZE144G+sdkvJmIUh3w0jMMDaqGM44ImNyynqy6ZetY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jDTiKqfKSd6hqXtnFOmBXxYcgU+zjHoSdjnLxzMXvMWS36ppp2Gij7vAuB10uc+XJ 1GcJ0qkQ/5xtivsivTZ37PYjRGYaXuDr2cXlzG9/8FVv/7QGYqIQekGW0k/vKEVEv2 YZnsZgf3ERs6SenpqaJQrP44FQHnfJQAzPXdGf+k= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Raoni Fassina Firmino , Nicholas Piggin , Michael Ellerman Subject: [PATCH 5.10 18/54] powerpc/64/signal: Fix regression in __kernel_sigtramp_rt64() semantics Date: Thu, 11 Feb 2021 16:02:02 +0100 Message-Id: <20210211150153.670452994@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210211150152.885701259@linuxfoundation.org> References: <20210211150152.885701259@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Raoni Fassina Firmino commit 24321ac668e452a4942598533d267805f291fdc9 upstream. Commit 0138ba5783ae ("powerpc/64/signal: Balance return predictor stack in signal trampoline") changed __kernel_sigtramp_rt64() VDSO and trampoline code, and introduced a regression in the way glibc's backtrace()[1] detects the signal-handler stack frame. Apart from the practical implications, __kernel_sigtramp_rt64() was a VDSO function with the semantics that it is a function you can call from userspace to end a signal handling. Now this semantics are no longer valid. I believe the aforementioned change affects all releases since 5.9. This patch tries to fix both the semantics and practical aspect of __kernel_sigtramp_rt64() returning it to the previous code, whilst keeping the intended behaviour of 0138ba5783ae by adding a new symbol to serve as the jump target from the kernel to the trampoline. Now the trampoline has two parts, a new entry point and the old return point. [1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-January/223194.html Fixes: 0138ba5783ae ("powerpc/64/signal: Balance return predictor stack in signal trampoline") Cc: stable@vger.kernel.org # v5.9+ Signed-off-by: Raoni Fassina Firmino Acked-by: Nicholas Piggin [mpe: Minor tweaks to change log formatting, add stable tag] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210201200505.iz46ubcizipnkcxe@work-tp Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/vdso.c | 2 +- arch/powerpc/kernel/vdso64/sigtramp.S | 11 ++++++++++- arch/powerpc/kernel/vdso64/vdso64.lds.S | 1 + 3 files changed, 12 insertions(+), 2 deletions(-) --- a/arch/powerpc/kernel/vdso.c +++ b/arch/powerpc/kernel/vdso.c @@ -475,7 +475,7 @@ static __init void vdso_setup_trampoline */ #ifdef CONFIG_PPC64 - vdso64_rt_sigtramp = find_function64(v64, "__kernel_sigtramp_rt64"); + vdso64_rt_sigtramp = find_function64(v64, "__kernel_start_sigtramp_rt64"); #endif vdso32_sigtramp = find_function32(v32, "__kernel_sigtramp32"); vdso32_rt_sigtramp = find_function32(v32, "__kernel_sigtramp_rt32"); --- a/arch/powerpc/kernel/vdso64/sigtramp.S +++ b/arch/powerpc/kernel/vdso64/sigtramp.S @@ -15,11 +15,20 @@ .text +/* + * __kernel_start_sigtramp_rt64 and __kernel_sigtramp_rt64 together + * are one function split in two parts. The kernel jumps to the former + * and the signal handler indirectly (by blr) returns to the latter. + * __kernel_sigtramp_rt64 needs to point to the return address so + * glibc can correctly identify the trampoline stack frame. + */ .balign 8 .balign IFETCH_ALIGN_BYTES -V_FUNCTION_BEGIN(__kernel_sigtramp_rt64) +V_FUNCTION_BEGIN(__kernel_start_sigtramp_rt64) .Lsigrt_start: bctrl /* call the handler */ +V_FUNCTION_END(__kernel_start_sigtramp_rt64) +V_FUNCTION_BEGIN(__kernel_sigtramp_rt64) addi r1, r1, __SIGNAL_FRAMESIZE li r0,__NR_rt_sigreturn sc --- a/arch/powerpc/kernel/vdso64/vdso64.lds.S +++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S @@ -150,6 +150,7 @@ VERSION __kernel_get_tbfreq; __kernel_sync_dicache; __kernel_sync_dicache_p5; + __kernel_start_sigtramp_rt64; __kernel_sigtramp_rt64; __kernel_getcpu; __kernel_time;