From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:40807 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756774AbcCDBm6 (ORCPT ); Thu, 3 Mar 2016 20:42:58 -0500 Subject: Patch "parisc: Fix ptrace syscall number and return value modification" has been added to the 4.4-stable tree To: deller@gmx.de, gregkh@linuxfoundation.org, vapier@gentoo.org Cc: , From: Date: Thu, 03 Mar 2016 17:42:57 -0800 Message-ID: <1457055777164112@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled parisc: Fix ptrace syscall number and return value modification to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: parisc-fix-ptrace-syscall-number-and-return-value-modification.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 98e8b6c9ac9d1b1e9d1122dfa6783d5d566bb8f7 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Tue, 19 Jan 2016 16:08:49 +0100 Subject: parisc: Fix ptrace syscall number and return value modification From: Helge Deller commit 98e8b6c9ac9d1b1e9d1122dfa6783d5d566bb8f7 upstream. Mike Frysinger reported that his ptrace testcase showed strange behaviour on parisc: It was not possible to avoid a syscall and the return value of a syscall couldn't be changed. To modify a syscall number, we were missing to save the new syscall number to gr20 which is then picked up later in assembly again. The effect that the return value couldn't be changed is a side-effect of another bug in the assembly code. When a process is ptraced, userspace expects each syscall to report entrance and exit of a syscall. If a syscall number was given which doesn't exist, we jumped to the normal syscall exit code instead of informing userspace that the (non-existant) syscall exits. This unexpected behaviour confuses userspace and thus the bug was misinterpreted as if we can't change the return value. This patch fixes both problems and was tested on 64bit kernel with 32bit userspace. Signed-off-by: Helge Deller Cc: Mike Frysinger Tested-by: Mike Frysinger Signed-off-by: Greg Kroah-Hartman --- arch/parisc/kernel/ptrace.c | 16 +++++++++++----- arch/parisc/kernel/syscall.S | 5 ++++- 2 files changed, 15 insertions(+), 6 deletions(-) --- a/arch/parisc/kernel/ptrace.c +++ b/arch/parisc/kernel/ptrace.c @@ -269,14 +269,19 @@ long compat_arch_ptrace(struct task_stru long do_syscall_trace_enter(struct pt_regs *regs) { - long ret = 0; - /* Do the secure computing check first. */ secure_computing_strict(regs->gr[20]); if (test_thread_flag(TIF_SYSCALL_TRACE) && - tracehook_report_syscall_entry(regs)) - ret = -1L; + 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. + */ + regs->gr[20] = -1UL; + goto out; + } #ifdef CONFIG_64BIT if (!is_compat_task()) @@ -290,7 +295,8 @@ long do_syscall_trace_enter(struct pt_re regs->gr[24] & 0xffffffff, regs->gr[23] & 0xffffffff); - return ret ? : regs->gr[20]; +out: + return regs->gr[20]; } void do_syscall_trace_exit(struct pt_regs *regs) --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -343,7 +343,7 @@ tracesys_next: #endif comiclr,>>= __NR_Linux_syscalls, %r20, %r0 - b,n .Lsyscall_nosys + b,n .Ltracesys_nosys LDREGX %r20(%r19), %r19 @@ -359,6 +359,9 @@ tracesys_next: be 0(%sr7,%r19) ldo R%tracesys_exit(%r2),%r2 +.Ltracesys_nosys: + ldo -ENOSYS(%r0),%r28 /* set errno */ + /* Do *not* call this function on the gateway page, because it makes a direct call to syscall_trace. */ Patches currently in stable-queue which might be from deller@gmx.de are queue-4.4/parisc-fix-ptrace-syscall-number-and-return-value-modification.patch