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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 7CF62C433EA for ; Mon, 20 Jul 2020 15:55:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50A7C206E9 for ; Mon, 20 Jul 2020 15:55:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595260508; bh=73OfyVQhcIxZMzuwA5a7Od8723BMHesLMf45Xpthq9M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=E+SrgbXvdo0+PQklMh35UD21pB0QXj9DnDDugQGArndzeu7VOcGGycTe9cXkz3TzB sIgjTvSu3NMgPjOfekqcF5u57e2DpdqW/sfYVcITukvGhT3VHqUKbQE9/0zn92bBiN r40T681kJw87rwckk39MTB3I02Lj/0S+1b7YuvGQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731626AbgGTPzH (ORCPT ); Mon, 20 Jul 2020 11:55:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:54034 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731404AbgGTPzF (ORCPT ); Mon, 20 Jul 2020 11:55:05 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 475CC2065E; Mon, 20 Jul 2020 15:55:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595260504; bh=73OfyVQhcIxZMzuwA5a7Od8723BMHesLMf45Xpthq9M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=meHayuuyAKG90IElWwBDPzn2RbK+hx1/2nYV+Ob9/PI646xzKrSXEAA5Pkk1GZt7l FDDv0hWNwuYc+9/tEtTA9xS0Fpr431k0tYbJWR0YhEwUY0UDwwvgBxwhwW17IQoXBF uVCi9CsvMbyGmRKmvh3o65sazw+dGIuqhq2jhNqw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mark Rutland , Keno Fischer , Luis Machado , Will Deacon Subject: [PATCH 4.19 126/133] arm64: compat: Ensure upper 32 bits of x0 are zero on syscall return Date: Mon, 20 Jul 2020 17:37:53 +0200 Message-Id: <20200720152809.812865589@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200720152803.732195882@linuxfoundation.org> References: <20200720152803.732195882@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Will Deacon commit 15956689a0e60aa0c795174f3c310b60d8794235 upstream. Although we zero the upper bits of x0 on entry to the kernel from an AArch32 task, we do not clear them on the exception return path and can therefore expose 64-bit sign extended syscall return values to userspace via interfaces such as the 'perf_regs' ABI, which deal exclusively with 64-bit registers. Explicitly clear the upper 32 bits of x0 on return from a compat system call. Cc: Cc: Mark Rutland Cc: Keno Fischer Cc: Luis Machado Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/syscall.h | 12 +++++++++++- arch/arm64/kernel/syscall.c | 3 +++ 2 files changed, 14 insertions(+), 1 deletion(-) --- a/arch/arm64/include/asm/syscall.h +++ b/arch/arm64/include/asm/syscall.h @@ -45,6 +45,10 @@ static inline long syscall_get_error(str struct pt_regs *regs) { unsigned long error = regs->regs[0]; + + if (is_compat_thread(task_thread_info(task))) + error = sign_extend64(error, 31); + return IS_ERR_VALUE(error) ? error : 0; } @@ -58,7 +62,13 @@ static inline void syscall_set_return_va struct pt_regs *regs, int error, long val) { - regs->regs[0] = (long) error ? error : val; + if (error) + val = error; + + if (is_compat_thread(task_thread_info(task))) + val = lower_32_bits(val); + + regs->regs[0] = val; } #define SYSCALL_MAX_ARGS 6 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -50,6 +50,9 @@ static void invoke_syscall(struct pt_reg ret = do_ni_syscall(regs, scno); } + if (is_compat_task()) + ret = lower_32_bits(ret); + regs->regs[0] = ret; }