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

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Dec 02, 2013 at 06:32:51PM +0200, Mika Kuoppala wrote:
> 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.

I guess a quick comment to explain that in the code would help. Can you
please update the patch?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch