Re: [PATCH] arch/x86: fix out-of-bounds in get_wchan()

[Andrey Ryabinin]

2015-09-28 12:00 GMT+03:00 Dmitry Vyukov <dvyukov@xxxxxxxxxx>:
>         stack = (unsigned long)task_stack_page(p);
> -       if (p->thread.sp < stack || p->thread.sp >= stack+THREAD_SIZE)
> +       /* The task can be already running at this point, so tread carefully. */
> +       fp = READ_ONCE(p->thread.sp);
> +       if (fp < stack || fp >= stack+THREAD_SIZE)

Since we deference fp, it should be "|| fp + sizeof(u64) >= stack + THREAD_SIZE"

>                 return 0;
> -       fp = *(u64 *)(p->thread.sp);
> +       fp = READ_ONCE(*(u64 *)fp);
>         do {
>                 if (fp < (unsigned long)stack ||
> -                   fp >= (unsigned long)stack+THREAD_SIZE)
> +                   fp+8 >= (unsigned long)stack+THREAD_SIZE)

The same as above;
        'fp+8 +sizeof(u64) >= ...'

>                         return 0;
> -               ip = *(u64 *)(fp+8);
> +               ip = READ_ONCE(*(u64 *)(fp+8));
>
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