From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id AF9BD6B038B for ; Tue, 21 Mar 2017 13:51:19 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id r89so4477786pfi.1 for ; Tue, 21 Mar 2017 10:51:19 -0700 (PDT) Received: from EUR01-HE1-obe.outbound.protection.outlook.com (mail-he1eur01on0124.outbound.protection.outlook.com. [104.47.0.124]) by mx.google.com with ESMTPS id f16si22098433pli.29.2017.03.21.10.51.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 21 Mar 2017 10:51:18 -0700 (PDT) From: Dmitry Safonov Subject: [PATCHv3] x86/mm: set x32 syscall bit in SET_PERSONALITY() Date: Tue, 21 Mar 2017 20:47:11 +0300 Message-ID: <20170321174711.29880-1-dsafonov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: 0x7f454c46@gmail.com, Dmitry Safonov , 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 , Thomas Gleixner After my changes to mmap(), its code now relies on the bitness of performing syscall. According to that, it chooses the base of allocation: mmap_base for 64-bit mmap() and mmap_compat_base for 32-bit syscall. It was done by: commit 1b028f784e8c ("x86/mm: Introduce mmap_compat_base() for 32-bit mmap()"). The code afterwards relies on in_compat_syscall() returning true for 32-bit syscalls. It's usually so while we're in context of application that does 32-bit syscalls. But during exec() it is not valid for x32 ELF. The reason is that the application hasn't yet done any syscall, so x32 bit has not being set. That results in -ENOMEM for x32 ELF files as there fired BAD_ADDR() in elf_map(), that is called from do_execve()->load_elf_binary(). For i386 ELFs it works as SET_PERSONALITY() sets TS_COMPAT flag. Set x32 bit before first return to userspace, during setting personality at exec(). This way we can rely on in_compat_syscall() during exec(). Do also the reverse: drop x32 syscall bit at SET_PERSONALITY for 64-bits. Fixes: commit 1b028f784e8c ("x86/mm: Introduce mmap_compat_base() for 32-bit mmap()") Cc: 0x7f454c46@gmail.com Cc: linux-mm@kvack.org Cc: Andrei Vagin Cc: Cyrill Gorcunov Cc: Borislav Petkov Cc: "Kirill A. Shutemov" Cc: x86@kernel.org Cc: H. Peter Anvin Cc: Andy Lutomirski Cc: Ingo Molnar Cc: Thomas Gleixner Reported-by: Adam Borowski Signed-off-by: Dmitry Safonov --- v2: - specifying mmap() allocation path which failed during exec() - fix comment style v3: - clear x32 syscall flag during x32 -> x86-64 exec() (thanks, HPA). arch/x86/kernel/process_64.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index d6b784a5520d..b03f186369eb 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -493,6 +493,8 @@ void set_personality_64bit(void) clear_thread_flag(TIF_IA32); clear_thread_flag(TIF_ADDR32); clear_thread_flag(TIF_X32); + /* Drop x32 syscall bit, so in_compat_syscall() will return false. */ + task_pt_regs(current)->orig_ax &= ~__X32_SYSCALL_BIT; /* Ensure the corresponding mm is not marked. */ if (current->mm) @@ -519,8 +521,14 @@ void set_personality_ia32(bool 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 */ + /* + * in_compat_syscall() uses the presence of the x32 + * syscall bit flag to determine compat status. + * On the bitness of syscall relies x86 mmap() code, + * so set x32 syscall bit right here to make + * in_compat_syscall() work during exec(). + */ + task_pt_regs(current)->orig_ax |= __X32_SYSCALL_BIT; current->thread.status &= ~TS_COMPAT; } else { set_thread_flag(TIF_IA32); -- 2.12.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org