Re: [MIPS] TLB handler fix for vmalloc'ed addresses

[Ralf Baechle <ralf@linux-mips.org>]

On Thu, Sep 10, 2009 at 06:37:47PM +0400, Maxim Uvarov wrote:

>>> TLB exception handler incorrecly handles situation
>>> with wrong vmalloc'ed addresses.  This patch adds
>>> verifications for vmalloc'ed addresses (similar to
>>> x86_64 implementation). So the code now traps inside
>>> do_page_fault() on access to the wrong area.
>>>
>>> Signed-off-by: Maxim Uvarov <muvarov@ru.mvista.com>
>>>
>>> Test case:
>>>
>>> #include <linux/module.h>
>>> #include <linux/init.h>
>>> #include <linux/kernel.h>
>>> #include <linux/kthread.h>
>>> #include <linux/delay.h>
>>>
>>> static struct task_struct *ts;
>>> static int example_thread(void *dummy)
>>> {
>>> 	void *ptr;
>>> 	ptr = vmalloc(16*1024*1024);
>>> 	for(;;)
>>> 	{
>>> 		msleep(100);
>>> 	}
>>> }
>>
>> So your test case allocates vmalloc memory but never touches it.
>
> Yes, it is so. Bug occurs on rmmod this module. (Module does not free memory
> allocated with vmalloc().

Nor does it stop the thread on exit or avoid unloading.  So panicing is
expected.

  Ralf