From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755990AbaFPVzD (ORCPT ); Mon, 16 Jun 2014 17:55:03 -0400 Received: from mail-ve0-f182.google.com ([209.85.128.182]:53705 "EHLO mail-ve0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755352AbaFPVzB (ORCPT ); Mon, 16 Jun 2014 17:55:01 -0400 MIME-Version: 1.0 In-Reply-To: <539F6646.4040605@zytor.com> References: <539F1C59.6070308@gmx.de> <539F297F.7010904@nod.at> <539F2B2D.6050105@gmx.de> <539F3077.7040005@gmx.de> <539F35A0.2050002@gmx.de> <539F567F.2050802@gmx.de> <539F5702.5050104@nod.at> <539F6646.4040605@zytor.com> From: Andy Lutomirski Date: Mon, 16 Jun 2014 14:54:40 -0700 Message-ID: Subject: Re: 3.15: kernel BUG at kernel/auditsc.c:1525! To: "H. Peter Anvin" Cc: Richard Weinberger , X86 ML , =?UTF-8?Q?Toralf_F=C3=B6rster?= , Eric Paris , Linux Kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 16, 2014 at 2:48 PM, H. Peter Anvin wrote: > On 06/16/2014 02:35 PM, Andy Lutomirski wrote: >> >> To hpa, etc: It appears that entry_32.S is missing any call to the >> audit exit hook on the badsys path. If I'm diagnosing this bug report >> correctly, this causes OOPSes. >> >> The the world at large: it's increasingly apparent that no one (except >> maybe the blackhats) has ever scrutinized the syscall auditing code. >> This is two old severe bugs in the code that have probably been there >> for a long time. >> > > Yes, the audit code is a total mess. > >> The bad syscall nr paths are their own incomprehensible route >> through the entry control flow. Rearrange them to work just like >> syscalls that return -ENOSYS. > > I have to admit... it sort of lends itself to a solution like this: > > /* For the 64-bit case, analogous code for 32 bits */ > movl $__NR_syscall_max+1,%ecx # *Not* __NR_syscall_max > cmpq %rcx,%rax > cmovae %rcx,%rax > movq %r10,%rcx > call *sys_call_table(,%rax,8) > > ... and having an extra (invalid) system call slot in the syscall table > beyond the end instead of branching off separately. > > (Note: we could use either cmova or cmovae, and either the 32- or 64-bit > form... the reason why is left as an exercise to the reader.) For 64-bit, I want to do this instead: https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/seccomp-fastpath&id=a5ec2d7af2c54b55fc7201fa662138b53fbbda39 I see no reason why the 64-bit badsys code needs its own code path at all. I haven't sent it yet because AFAICT it doesn't fix any bug, and the series it's a part of isn't ready. I'm also contemplating rewriting the 64-bit syscall entry work path in C. --Andy