linux-kernel - [PATCH 2/3] x86_64, ptrace: Remove checks for TIF

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Message-Id: <71c7ab36456855d11ae07edd4945a7dfe80f9915.1424822291.git.luto@amacapital.net>
Date:	Tue, 24 Feb 2015 16:01:38 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...capital.net>
Subject: [PATCH 2/3] x86_64, 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>
---
 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 e510618b2e91..1e125817cf9f 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;
 	}
 
-- 
2.3.0

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