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 85800C433F8 for ; Mon, 20 Jul 2020 16:05:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63C5B2064B for ; Mon, 20 Jul 2020 16:05:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595261138; bh=L5RiK5AUlbXgr5VqCx8Xe5ofd/ZjjQoDI6iJqP7wBqo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=jMgQvC7aLEQ083pgQTE7yodxs805lCK1jWOohddl6cCR8Qsa7FeZGMzv6va+i46wt 5Y9Vyl/tpL6jzrdiDtyO67SXJ1/c6f30SYUdZV9tMpuAVhzGOs6Bt8HkF/qyoG6d2h HuP8pvM4FtS/LfyhaYfE4hx8OvLIhIuk98x36r7k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732989AbgGTQFg (ORCPT ); Mon, 20 Jul 2020 12:05:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:41040 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732984AbgGTQF3 (ORCPT ); Mon, 20 Jul 2020 12:05:29 -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 5995D2065E; Mon, 20 Jul 2020 16:05:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595261128; bh=L5RiK5AUlbXgr5VqCx8Xe5ofd/ZjjQoDI6iJqP7wBqo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JcrbH5dWFrUINUh+2M/RhWMPcrJgtFz3MT8RVQa0T2prIqoGfpdUyWcVYLaRrdJmR rgBv9Iwqr+L1DzA9z4UsIEsu54hLj145b6R0crB3T5IY+dMQgrCCdiepMVumnE7W9o kH2KHIg5HSWM13ofDnfsp/fTxMLfzqFx7JcE10PI= 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 5.4 201/215] arm64: compat: Ensure upper 32 bits of x0 are zero on syscall return Date: Mon, 20 Jul 2020 17:38:03 +0200 Message-Id: <20200720152829.727816221@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200720152820.122442056@linuxfoundation.org> References: <20200720152820.122442056@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: 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 @@ -34,6 +34,10 @@ 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; } @@ -47,7 +51,13 @@ 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; }