linux-kernel - [RFC PATCH 1/5] x86: add user_mode_vm check in stack_overflow

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Date:	Mon, 07 Nov 2011 14:52:35 +0900
From:	Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Randy Dunlap <rdunlap@...otime.net>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, yrl.pp-manager.tt@...achi.com,
	Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [RFC PATCH 1/5] x86: add user_mode_vm check in stack_overflow_check

The kernel stack overflow is checked in stack_overflow_check(),
which may wrongly detect the overflow if the stack pointer
pointed to the kernel stack accidentally.

This patch adds user-mode-vm checking before it to avoid this
misdetection and bails out early if the user stack is used.

Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
---

 arch/x86/kernel/irq_64.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index acf8fbf..69bca46 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -38,6 +38,9 @@ static inline void stack_overflow_check(struct pt_regs *regs)
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
 	u64 curbase = (u64)task_stack_page(current);
 
+	if (user_mode_vm(regs))
+		return;
+
 	WARN_ONCE(regs->sp >= curbase &&
 		  regs->sp <= curbase + THREAD_SIZE &&
 		  regs->sp <  curbase + sizeof(struct thread_info) +

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