Re: [PATCH] tests/gem_reset_stats: add close-pending-fork

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> On Mon, Dec 02, 2013 at 04:47:46PM +0200, Mika Kuoppala wrote:
>> Fork and create another filedesc to wait access to already
>> hung GPU and then kill it. This triggers use after free of the
>> request->batch_obj.
>> 
>> Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
>> ---
>> +static int __test_open_any(void)
>> +{
>> +	char *name;
>> +	int ret, fd;
>> +
>> +	ret = asprintf(&name, "/dev/dri/card%d", drm_get_card());
>> +	if (ret == -1)
>> +		return -1;
>> +
>> +	fd = open(name, O_RDWR);
>> +	free(name);
>> +
>> +	return fd;
>> +}
>> +
>> +static void test_close_pending_fork(void)
>> +{
>> +	int pid;
>> +	int fd, fd2, h;
>> +
>> +	fd = drm_open_any();
>> +	igt_assert(fd >= 0);
>
> [snip]
>
>> +	close(fd);
>> +
>> +	fd = drm_open_any();
>
> This breaks the testsuite since drm_open_any() will now return the
> closed fd. Hence your __test_open_any() above.
>
> However this does not justify kernel doing anything other than terminating
> your process with extreme prejudice.

I discussed this with Chris in IRC. There seems to be no problem
as drm_open_any doesn't cache file descriptors.

The reason i use __test_open_any is that I needed a way to bypass
testsuites exit handling.

--Mika