Re: [patch 08/11] Modify Ptrace routines to access breakpoint registers

[Ingo Molnar <mingo@elte.hu>]

* prasad@linux.vnet.ibm.com <prasad@linux.vnet.ibm.com> wrote:

> -static unsigned long debugreg_addr_limit(struct task_struct *task)
> -{
> -#ifdef CONFIG_IA32_EMULATION
> -	if (test_tsk_thread_flag(task, TIF_IA32))
> -		return IA32_PAGE_OFFSET - 3;
> -#endif
> -	return TASK_SIZE_MAX - 7;
> -}
> -

I dont see where this security check has been carried over into 
the generic code. The new code has:

 +int arch_check_va_in_userspace(unsigned long va, struct task_struct *tsk)
 +{
 +       return (va < TASK_SIZE);
 +}

but i think that misses the detail that it's not just the start 
address of an x86 breakpoint that has to be considered, but also 
the end addess of it.

For example a hardware breakpoint can be at 0xbfffffff with a 
length of 4 bytes - thus overlapping into kernel-space by 3 
bytes. It is important to not let that happen.

	Ingo