linux-kernel - [PATCH 2/9] x86, perf: Fix incorrect TIF_IA32 check in code_segment

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Date:	Wed, 18 Mar 2015 18:33:28 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Brad Spengler <spender@...ecurity.net>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 2/9] x86, perf: Fix incorrect TIF_IA32 check in code_segment_base

We're want to check whether user code is in 32-bit mode, not whether
the task is nominally 32-bit.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/kernel/cpu/perf_event.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index b71a7f86d68a..979963bb3977 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2161,10 +2161,9 @@ static unsigned long code_segment_base(struct pt_regs *regs)
 	if (user_mode(regs) && regs->cs != __USER_CS)
 		return get_segment_base(regs->cs);
 #else
-	if (test_thread_flag(TIF_IA32)) {
-		if (user_mode(regs) && regs->cs != __USER32_CS)
-			return get_segment_base(regs->cs);
-	}
+	if (user_mode(regs) && !user_64bit_mode(regs) &&
+	    regs->cs != __USER32_CS)
+		return get_segment_base(regs->cs);
 #endif
 	return 0;
 }
-- 
2.3.0

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