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 in
user space points to the kernel stack intentionally or
accidentally. So, the actual overflow is never detected after
this misdetection because WARN_ONCE() is used on the detection
of it.

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

Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: Randy Dunlap <rdunlap@xenotime.net>
Link: http://lkml.kernel.org/r/20111129060821.11076.55315.stgit@ltc219.sdl.hitachi.co.jp
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>

diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index acf8fbf8fbda1960de6cbd18eaf47a0a049eed8b..69bca468c47a8ffc22ea5811cb3bdf63caf0f44b 100644 (file)
--- 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) +