ARM64: check stack pointer in get_wchan

get_wchan() is lockless. Task may wakeup at any time and change its own stack,
thus each next stack frame may be overwritten and filled with random stuff.

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index de17c89..0adb8f0 100644 (file)
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -308,6 +308,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
 unsigned long get_wchan(struct task_struct *p)
 {
        struct stackframe frame;
+       unsigned long stack_page;
        int count = 0;
        if (!p || p == current || p->state == TASK_RUNNING)
                return 0;
@@ -315,9 +316,11 @@ unsigned long get_wchan(struct task_struct *p)
        frame.fp = thread_saved_fp(p);
        frame.sp = thread_saved_sp(p);
        frame.pc = thread_saved_pc(p);
+       stack_page = (unsigned long)task_stack_page(p);
        do {
-               int ret = unwind_frame(&frame);
-               if (ret < 0)
+               if (frame.sp < stack_page ||
+                   frame.sp >= stack_page + THREAD_SIZE ||
+                   unwind_frame(&frame))
                        return 0;
                if (!in_sched_functions(frame.pc))
                        return frame.pc;