Re: [PATCH] arm64: disable kasan when accessing frame->fp in unwind_frame

[Shi, Yang]

On 2/8/2016 12:51 AM, Andrey Ryabinin wrote:


On 02/06/2016 02:04 AM, Yang Shi wrote:

  #include <asm/irq.h>
  #include <asm/stacktrace.h>
@@ -64,7 +65,9 @@ int notrace unwind_frame(struct task_struct *tsk, struct 
stackframe *frame)
                return -EINVAL;

        frame->sp = fp + 0x10;
+       kasan_disable_current();
        frame->fp = *(unsigned long *)(fp);

It would be better to use READ_ONCE_NOCHECK() here.
See f7d27c35ddff7 ("x86/mm, kasan: Silence KASAN warnings in get_wchan()") 
which solves the same problem for x86.

Thanks for the suggestion, I'm going to try it soon.


+       kasan_enable_current();
        frame->pc = *(unsigned long *)(fp + 8);

Why you left frame->pc out of scope? This line could trigger kasan as well.

Actually, it was not reported as frequently as the first one. In my 
first a couple of boot test, it was not triggered before I came up with 
the patch. The first one is triggered every time.

It will be fixed in v2 too.

Thanks,
Yang



  #ifdef CONFIG_FUNCTION_GRAPH_TRACER