Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933111AbbFPJWx (ORCPT ); Tue, 16 Jun 2015 05:22:53 -0400 Received: from mail.kernel.org ([198.145.29.136]:55483 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756467AbbFPIoU (ORCPT ); Tue, 16 Jun 2015 04:44:20 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Borislav Petkov , Denys Vlasenko , "H. Peter Anvin" , Linus Torvalds , Oleg Nesterov , Thomas Gleixner , Ingo Molnar , Zefan Li Subject: [PATCH 3.4 072/172] x86/asm/entry/64: Remove a bogus 'ret_from_fork' optimization Date: Tue, 16 Jun 2015 16:35:26 +0800 Message-Id: <1434443826-4929-72-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434443587-4599-1-git-send-email-lizf@kernel.org> References: <1434443587-4599-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2271 Lines: 65 From: Andy Lutomirski 3.4.108-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 956421fbb74c3a6261903f3836c0740187cf038b upstream. '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 Link: http://lkml.kernel.org/r/4710be56d76ef994ddf59087aad98c000fbab9a4.1424989793.git.luto@amacapital.net [ Backported from tip:x86/asm. ] Signed-off-by: Ingo Molnar Signed-off-by: Zefan Li --- 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 45f9c70..8b49131 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -414,11 +414,14 @@ ENTRY(ret_from_fork) testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread? jz retint_restore_args - 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 CFI_ENDPROC END(ret_from_fork) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/