From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 0FCCD6B039F for ; Tue, 28 Mar 2017 09:02:42 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id o123so102210297pga.16 for ; Tue, 28 Mar 2017 06:02:42 -0700 (PDT) Received: from EUR01-HE1-obe.outbound.protection.outlook.com (mail-he1eur01on0117.outbound.protection.outlook.com. [104.47.0.117]) by mx.google.com with ESMTPS id t25si4153071pgo.353.2017.03.28.06.02.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 28 Mar 2017 06:02:41 -0700 (PDT) Subject: Re: [PATCHv3] x86/mm: set x32 syscall bit in SET_PERSONALITY() References: <20170321174711.29880-1-dsafonov@virtuozzo.com> From: Dmitry Safonov Message-ID: <66372d92-8fc1-301e-df21-7020514d7dbb@virtuozzo.com> Date: Tue, 28 Mar 2017 15:59:00 +0300 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner 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 On 03/28/2017 03:51 PM, Thomas Gleixner wrote: > 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. Ok, I'll check the ifdeffery, define __NR_{x32_,ia32_}execve, test it and resend v4 today or tomorrow. Thanks. > > 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); > > -- Dmitry -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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