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Subject[RFC PATCH 1/5] x86: add user_mode_vm check in stack_overflow_check
Date
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@hitachi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.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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