From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755357AbbCELuC (ORCPT ); Thu, 5 Mar 2015 06:50:02 -0500 Received: from terminus.zytor.com ([198.137.202.10]:47832 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751404AbbCELt7 (ORCPT ); Thu, 5 Mar 2015 06:49:59 -0500 Date: Thu, 5 Mar 2015 03:49:22 -0800 From: tip-bot for Andy Lutomirski Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, dvlasenk@redhat.com, oleg@redhat.com, bp@alien8.de, stable@vger.kernel.org, luto@amacapital.net, torvalds@linux-foundation.org, tglx@linutronix.de, mingo@kernel.org Reply-To: tglx@linutronix.de, mingo@kernel.org, torvalds@linux-foundation.org, luto@amacapital.net, stable@vger.kernel.org, hpa@zytor.com, oleg@redhat.com, bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org In-Reply-To: <4710be56d76ef994ddf59087aad98c000fbab9a4.1424989793.git.luto@amacapital.net> References: <4710be56d76ef994ddf59087aad98c000fbab9a4.1424989793.git.luto@amacapital.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/asm/entry/64: Remove a bogus 'ret_from_fork' optimization Git-Commit-ID: 956421fbb74c3a6261903f3836c0740187cf038b X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 956421fbb74c3a6261903f3836c0740187cf038b Gitweb: http://git.kernel.org/tip/956421fbb74c3a6261903f3836c0740187cf038b Author: Andy Lutomirski AuthorDate: Thu, 5 Mar 2015 01:09:44 +0100 Committer: Ingo Molnar CommitDate: Thu, 5 Mar 2015 01:12:23 +0100 x86/asm/entry/64: Remove a bogus 'ret_from_fork' optimization 'ret_from_fork' checks TIF_IA32 to determine whether 'pt_regs' and the related state make sense for 'ret_from_sys_call'. This is entirely the wrong check. TS_COMPAT would make a little more sense, but there's really no point in keeping this optimization at all. This fixes a return to the wrong user CS if we came from int 0x80 in a 64-bit task. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Thomas Gleixner Cc: Link: http://lkml.kernel.org/r/4710be56d76ef994ddf59087aad98c000fbab9a4.1424989793.git.luto@amacapital.net [ Backported from tip:x86/asm. ] Signed-off-by: Ingo Molnar --- arch/x86/kernel/entry_64.S | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 10074ad..1d74d16 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -269,11 +269,14 @@ ENTRY(ret_from_fork) testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread? jz 1f - testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET - jnz int_ret_from_sys_call - - RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET - jmp ret_from_sys_call # go to the SYSRET fastpath + /* + * By the time we get here, we have no idea whether our pt_regs, + * ti flags, and ti status came from the 64-bit SYSCALL fast path, + * the slow path, or one of the ia32entry paths. + * Use int_ret_from_sys_call to return, since it can safely handle + * all of the above. + */ + jmp int_ret_from_sys_call 1: subq $REST_SKIP, %rsp # leave space for volatiles