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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,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 06FCBC43381 for ; Mon, 25 Feb 2019 21:26:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C985720C01 for ; Mon, 25 Feb 2019 21:26:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551129965; bh=rKFSH2QolR2zpUpUr/7RhH3ednBoGtVW7INDd+u+34o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=cEG1HBXxnB3EV0WdLfSFwKqI4GzY8As9eLrkXmf5hRbMo6Z/Bg5a3UZpGztN0RUrI N3tK7jkL6ShnM3uMHcm9SKrYOGfK4yLQK2m8Ffp7pWbZPCtZeN9u4gRtN2JF3drqNG XE6B0KELJxptnMf5qsQZoNcFPSrXyjk/CdJxff1w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731518AbfBYV0E (ORCPT ); Mon, 25 Feb 2019 16:26:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:60444 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731132AbfBYV0B (ORCPT ); Mon, 25 Feb 2019 16:26:01 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 B5249213A2; Mon, 25 Feb 2019 21:25:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551129960; bh=rKFSH2QolR2zpUpUr/7RhH3ednBoGtVW7INDd+u+34o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PbXyM8QRizL3NWw2spgO+RMqYY3G2g2bqucflcjP+bfkY3s1VoBXN+WMeGdqnBPl+ AuJLT6HcwnrKd2L8QD82HpEEsx/Sh9+4+USdQ6bSX+Gu/6TEQa0xGpriV8ZOL+jagB AefUI2eX51zNc538Rj4UL1+H3KZlDBHVKvVyfhSQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Dmitry V. Levin" , Helge Deller Subject: [PATCH 4.19 122/152] parisc: Fix ptrace syscall number modification Date: Mon, 25 Feb 2019 22:11:54 +0100 Message-Id: <20190225195051.515861581@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190225195043.645958524@linuxfoundation.org> References: <20190225195043.645958524@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 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dmitry V. Levin commit b7dc5a071ddf69c0350396b203cba32fe5bab510 upstream. Commit 910cd32e552e ("parisc: Fix and enable seccomp filter support") introduced a regression in ptrace-based syscall tampering: when tracer changes syscall number to -1, the kernel fails to initialize %r28 with -ENOSYS and subsequently fails to return the error code of the failed syscall to userspace. This erroneous behaviour could be observed with a simple strace syscall fault injection command which is expected to print something like this: $ strace -a0 -ewrite -einject=write:error=enospc echo hello write(1, "hello\n", 6) = -1 ENOSPC (No space left on device) (INJECTED) write(2, "echo: ", 6) = -1 ENOSPC (No space left on device) (INJECTED) write(2, "write error", 11) = -1 ENOSPC (No space left on device) (INJECTED) write(2, "\n", 1) = -1 ENOSPC (No space left on device) (INJECTED) +++ exited with 1 +++ After commit 910cd32e552ea09caa89cdbe328e468979b030dd it loops printing something like this instead: write(1, "hello\n", 6../strace: Failed to tamper with process 12345: unexpectedly got no error (return value 0, error 0) ) = 0 (INJECTED) This bug was found by strace test suite. Fixes: 910cd32e552e ("parisc: Fix and enable seccomp filter support") Cc: stable@vger.kernel.org # v4.5+ Signed-off-by: Dmitry V. Levin Tested-by: Helge Deller Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman --- arch/parisc/kernel/ptrace.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) --- a/arch/parisc/kernel/ptrace.c +++ b/arch/parisc/kernel/ptrace.c @@ -308,15 +308,29 @@ long compat_arch_ptrace(struct task_stru long do_syscall_trace_enter(struct pt_regs *regs) { - if (test_thread_flag(TIF_SYSCALL_TRACE) && - tracehook_report_syscall_entry(regs)) { + if (test_thread_flag(TIF_SYSCALL_TRACE)) { + int rc = tracehook_report_syscall_entry(regs); + /* - * Tracing decided this syscall should not happen or the - * debugger stored an invalid system call number. Skip - * the system call and the system call restart handling. + * As tracesys_next does not set %r28 to -ENOSYS + * when %r20 is set to -1, initialize it here. */ - regs->gr[20] = -1UL; - goto out; + regs->gr[28] = -ENOSYS; + + if (rc) { + /* + * A nonzero return code from + * tracehook_report_syscall_entry() tells us + * to prevent the syscall execution. Skip + * the syscall call and the syscall restart handling. + * + * Note that the tracer may also just change + * regs->gr[20] to an invalid syscall number, + * that is handled by tracesys_next. + */ + regs->gr[20] = -1UL; + return -1; + } } /* Do the secure computing check after ptrace. */ @@ -340,7 +354,6 @@ long do_syscall_trace_enter(struct pt_re regs->gr[24] & 0xffffffff, regs->gr[23] & 0xffffffff); -out: /* * Sign extend the syscall number to 64bit since it may have been * modified by a compat ptrace call