linux-kernel - [tip:x86/asm] x86/ptrace: Remove checks for TIF

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Date:	Wed, 25 Feb 2015 00:27:40 -0800
From:	tip-bot for Andy Lutomirski <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, linux-kernel@...r.kernel.org, dvlasenk@...hat.com,
	mingo@...nel.org, bp@...en8.de, tglx@...utronix.de,
	luto@...capital.net
Subject: [tip:x86/asm] x86/ptrace:
  Remove checks for TIF_IA32 when changing CS and SS

Commit-ID:  08571f1ae327bfb631cb7171bde5ea605df626c6
Gitweb:     http://git.kernel.org/tip/08571f1ae327bfb631cb7171bde5ea605df626c6
Author:     Andy Lutomirski <luto@...capital.net>
AuthorDate: Tue, 24 Feb 2015 16:01:38 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 25 Feb 2015 08:27:49 +0100

x86/ptrace: Remove checks for TIF_IA32 when changing CS and SS

The ability for modified CS and/or SS to be useful has nothing
to do with TIF_IA32.  Similarly, if there's an exploit involving
changing CS or SS, it's exploitable with or without a TIF_IA32
check.

So just delete the check.

Signed-off-by: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Link: http://lkml.kernel.org/r/71c7ab36456855d11ae07edd4945a7dfe80f9915.1424822291.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/ptrace.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index e510618..1e12581 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -364,18 +364,12 @@ static int set_segment_reg(struct task_struct *task,
 	case offsetof(struct user_regs_struct,cs):
 		if (unlikely(value == 0))
 			return -EIO;
-#ifdef CONFIG_IA32_EMULATION
-		if (test_tsk_thread_flag(task, TIF_IA32))
-			task_pt_regs(task)->cs = value;
-#endif
+		task_pt_regs(task)->cs = value;
 		break;
 	case offsetof(struct user_regs_struct,ss):
 		if (unlikely(value == 0))
 			return -EIO;
-#ifdef CONFIG_IA32_EMULATION
-		if (test_tsk_thread_flag(task, TIF_IA32))
-			task_pt_regs(task)->ss = value;
-#endif
+		task_pt_regs(task)->ss = value;
 		break;
 	}
 
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