[Intel-gfx] [PATCH i-g-t 3/3] igt/gem_softpin: Add testcase for race between evict and close

[Michał Winiarski]

From: Artur Harasimiuk <artur.harasimiuk at intel.com>

It's possible to trigger a race between vma eviction and closing the
object backing it when handling colliding addresses, resulting in
use-after-free.

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Thomas Daniel <thomas.daniel at intel.com>
Signed-off-by: Artur Harasimiuk <artur.harasimiuk at intel.com>
Signed-off-by: Michał Winiarski <michal.winiarski at intel.com>
---
 tests/gem_softpin.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/tests/gem_softpin.c b/tests/gem_softpin.c
index 1a9ef02..d4613bc 100644
--- a/tests/gem_softpin.c
+++ b/tests/gem_softpin.c
@@ -27,6 +27,7 @@
  */
 
 #include "igt.h"
+#include <pthread.h>
 
 #define EXEC_OBJECT_PINNED	(1<<4)
 #define EXEC_OBJECT_SUPPORTS_48B_ADDRESS (1<<3)
@@ -471,6 +472,74 @@ static void test_noreloc(int fd, enum sleep sleep)
 		gem_close(fd, object[i].handle);
 }
 
+#define SOFTPIN_STRESS_LOOPS 100000
+
+struct evict_close_thread_data {
+	int fd;
+	int pipefd[2];
+	bool stop;
+	pthread_mutex_t mutex;
+};
+
+static void *evict_close_thread(void *data)
+{
+	struct evict_close_thread_data *t = (struct evict_close_thread_data*)data;
+	uint32_t handle;
+
+	pthread_mutex_lock(&t->mutex);
+	while (!t->stop) {
+		pthread_mutex_unlock(&t->mutex);
+		read(t->pipefd[0], &handle, sizeof(handle));
+		gem_close(t->fd, handle);
+		pthread_mutex_lock(&t->mutex);
+	}
+	pthread_mutex_unlock(&t->mutex);
+
+	return NULL;
+}
+
+static void test_evict_close_race(int fd)
+{
+	pthread_t t;
+	struct evict_close_thread_data t_data;
+	unsigned int loops = SOFTPIN_STRESS_LOOPS;
+	const uint32_t bbe = MI_BATCH_BUFFER_END;
+	struct drm_i915_gem_execbuffer2 execbuf;
+	struct drm_i915_gem_exec_object2 object;
+
+	memset(&execbuf, 0, sizeof(execbuf));
+	memset(&object, 0, sizeof(object));
+
+	execbuf.buffers_ptr = (uintptr_t)&object;
+	execbuf.buffer_count = 1;
+	object.flags = EXEC_OBJECT_PINNED;
+	object.offset = 0;
+
+	memset(&t_data, 0, sizeof(t_data));
+	t_data.fd = fd;
+	igt_assert(pthread_mutex_init(&t_data.mutex, NULL) == 0);
+	igt_assert(pipe(t_data.pipefd) == 0);
+
+	igt_assert(pthread_create(&t, NULL, evict_close_thread, &t_data) == 0);
+
+	while (loops--) {
+		object.handle = gem_create(fd, 4096);
+		gem_write(fd, object.handle, 0, &bbe, sizeof(bbe));
+		gem_execbuf(fd, &execbuf);
+		write(t_data.pipefd[1], &object.handle, sizeof(object.handle));
+	}
+
+	pthread_mutex_lock(&t_data.mutex);
+	t_data.stop = 1;
+	pthread_mutex_unlock(&t_data.mutex);
+
+	pthread_join(t, NULL);
+
+	close(t_data.pipefd[0]);
+	close(t_data.pipefd[1]);
+	pthread_mutex_destroy(&t_data.mutex);
+}
+
 igt_main
 {
 	int fd = -1;
@@ -507,6 +576,9 @@ igt_main
 	igt_subtest("evict-hang")
 		test_evict_hang(fd);
 
+	igt_subtest("stress-evict-close")
+		test_evict_close_race(fd);
+
 	igt_fixture
 		close(fd);
 }
-- 
2.8.0