Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933072AbdC1Mwm (ORCPT ); Tue, 28 Mar 2017 08:52:42 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:51563 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932306AbdC1Mwj (ORCPT ); Tue, 28 Mar 2017 08:52:39 -0400 Date: Tue, 28 Mar 2017 14:51:31 +0200 (CEST) From: Thomas Gleixner To: Dmitry Safonov cc: linux-kernel@vger.kernel.org, 0x7f454c46@gmail.com, Adam Borowski , linux-mm@kvack.org, Andrei Vagin , Cyrill Gorcunov , Borislav Petkov , "Kirill A. Shutemov" , x86@kernel.org, "H. Peter Anvin" , Andy Lutomirski , Ingo Molnar Subject: Re: [PATCHv3] x86/mm: set x32 syscall bit in SET_PERSONALITY() In-Reply-To: Message-ID: References: <20170321174711.29880-1-dsafonov@virtuozzo.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3452 Lines: 115 On Tue, 28 Mar 2017, Dmitry Safonov wrote: > On 03/22/2017 01:21 AM, Thomas Gleixner wrote: > > On Tue, 21 Mar 2017, Dmitry Safonov wrote: > > > v3: > > > - clear x32 syscall flag during x32 -> x86-64 exec() (thanks, HPA). > > > > For correctness sake, this wants to be cleared in the IA32 path as > > well. It's not causing any harm, but .... > > > > I'll amend the patch. > > So, just a gentle reminder about this problem. > Should I resend v4 with clearing x32 bit in ia32 path? > Or should I resend with this fixup: > https://lkml.org/lkml/2017/3/22/343 > > The fixup doesn't look as simple as clearing x32 syscall bit, but I may > be wrong. Something like the below should set it correctly for all possible scenarios. Thanks, tglx 8<------------------ arch/x86/kernel/process_64.c | 63 ++++++++++++++++++++++++++++--------------- 1 file changed, 42 insertions(+), 21 deletions(-) --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -494,6 +494,8 @@ void set_personality_64bit(void) clear_thread_flag(TIF_IA32); clear_thread_flag(TIF_ADDR32); clear_thread_flag(TIF_X32); + /* Pretend that this comes from a 64bit execve */ + task_pt_regs(current)->orig_ax = __NR_execve; /* Ensure the corresponding mm is not marked. */ if (current->mm) @@ -506,32 +508,51 @@ void set_personality_64bit(void) current->personality &= ~READ_IMPLIES_EXEC; } -void set_personality_ia32(bool x32) +static void __set_personality_x32(void) +{ +#ifdef CONFIG_X86_X32 + clear_thread_flag(TIF_IA32); + set_thread_flag(TIF_X32); + if (current->mm) + current->mm->context.ia32_compat = TIF_X32; + current->personality &= ~READ_IMPLIES_EXEC; + /* + * in_compat_syscall() uses the presence of the x32 + * syscall bit flag to determine compat status. + * The x86 mmap() code relies on the syscall bitness + * so set x32 syscall bit right here to make + * in_compat_syscall() work during exec(). + * + * Pretend to come from a x32 execve. + */ + task_pt_regs(current)->orig_ax = __NR_x32_execve | __X32_SYSCALL_BIT; + current->thread.status &= ~TS_COMPAT; +#endif +} + +static void __set_personality_ia32(void) { - /* inherit personality from parent */ +#ifdef CONFIG_COMPAT_32 + set_thread_flag(TIF_IA32); + clear_thread_flag(TIF_X32); + if (current->mm) + current->mm->context.ia32_compat = TIF_IA32; + current->personality |= force_personality32; + /* Prepare the first "return" to user space */ + task_pt_regs(current)->orig_ax = __NR_ia32_execve; + current->thread.status |= TS_COMPAT; +#endif +} +void set_personality_ia32(bool x32) +{ /* Make sure to be in 32bit mode */ set_thread_flag(TIF_ADDR32); - /* Mark the associated mm as containing 32-bit tasks. */ - if (x32) { - clear_thread_flag(TIF_IA32); - set_thread_flag(TIF_X32); - if (current->mm) - current->mm->context.ia32_compat = TIF_X32; - current->personality &= ~READ_IMPLIES_EXEC; - /* in_compat_syscall() uses the presence of the x32 - syscall bit flag to determine compat status */ - current->thread.status &= ~TS_COMPAT; - } else { - set_thread_flag(TIF_IA32); - clear_thread_flag(TIF_X32); - if (current->mm) - current->mm->context.ia32_compat = TIF_IA32; - current->personality |= force_personality32; - /* Prepare the first "return" to user space */ - current->thread.status |= TS_COMPAT; - } + if (x32) + __set_personality_x32(); + else + __set_personality_ia32(); } EXPORT_SYMBOL_GPL(set_personality_ia32);