[PATCH v2] drm/i915/selftests: Change mock_request() to return error pointers

[Dan Carpenter]

There was an error pointer vs NULL bug in __igt_breadcrumbs_smoketest().
The __mock_request_alloc() function implements the
smoketest->request_alloc() function pointer.  It was supposed to return
error pointers, but it propogates the NULL return from mock_request()
so in the event of a failure, it would lead to a NULL pointer
dereference.

To fix this, change the mock_request() function to return error pointers
and update all the callers to expect that.

Fixes: 52c0fdb25c7c ("drm/i915: Replace global breadcrumbs with per-context 
interrupt tracking")
Signed-off-by: Dan Carpenter <dan.carpen...@linaro.org>
---
V2: In v1 I just updated __mock_request_alloc() to return an error pointer
    but in v2, I changed mock_request() to update an error pointer and
    updated all the callers.  It's a more extensive change, but hopefully
    cleaner.

 drivers/gpu/drm/i915/selftests/i915_request.c | 20 +++++++++----------
 drivers/gpu/drm/i915/selftests/mock_request.c |  2 +-
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c 
b/drivers/gpu/drm/i915/selftests/i915_request.c
index 88870844b5bd..2fb7a9e7efec 100644
--- a/drivers/gpu/drm/i915/selftests/i915_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_request.c
@@ -73,8 +73,8 @@ static int igt_add_request(void *arg)
        /* Basic preliminary test to create a request and let it loose! */
 
        request = mock_request(rcs0(i915)->kernel_context, HZ / 10);
-       if (!request)
-               return -ENOMEM;
+       if (IS_ERR(request))
+               return PTR_ERR(request);
 
        i915_request_add(request);
 
@@ -91,8 +91,8 @@ static int igt_wait_request(void *arg)
        /* Submit a request, then wait upon it */
 
        request = mock_request(rcs0(i915)->kernel_context, T);
-       if (!request)
-               return -ENOMEM;
+       if (IS_ERR(request))
+               return PTR_ERR(request);
 
        i915_request_get(request);
 
@@ -160,8 +160,8 @@ static int igt_fence_wait(void *arg)
        /* Submit a request, treat it as a fence and wait upon it */
 
        request = mock_request(rcs0(i915)->kernel_context, T);
-       if (!request)
-               return -ENOMEM;
+       if (IS_ERR(request))
+               return PTR_ERR(request);
 
        if (dma_fence_wait_timeout(&request->fence, false, T) != -ETIME) {
                pr_err("fence wait success before submit (expected 
timeout)!\n");
@@ -219,8 +219,8 @@ static int igt_request_rewind(void *arg)
        GEM_BUG_ON(IS_ERR(ce));
        request = mock_request(ce, 2 * HZ);
        intel_context_put(ce);
-       if (!request) {
-               err = -ENOMEM;
+       if (IS_ERR(request)) {
+               err = PTR_ERR(request);
                goto err_context_0;
        }
 
@@ -237,8 +237,8 @@ static int igt_request_rewind(void *arg)
        GEM_BUG_ON(IS_ERR(ce));
        vip = mock_request(ce, 0);
        intel_context_put(ce);
-       if (!vip) {
-               err = -ENOMEM;
+       if (IS_ERR(vip)) {
+               err = PTR_ERR(vip);
                goto err_context_1;
        }
 
diff --git a/drivers/gpu/drm/i915/selftests/mock_request.c 
b/drivers/gpu/drm/i915/selftests/mock_request.c
index 09f747228dff..1b0cf073e964 100644
--- a/drivers/gpu/drm/i915/selftests/mock_request.c
+++ b/drivers/gpu/drm/i915/selftests/mock_request.c
@@ -35,7 +35,7 @@ mock_request(struct intel_context *ce, unsigned long delay)
        /* NB the i915->requests slab cache is enlarged to fit mock_request */
        request = intel_context_create_request(ce);
        if (IS_ERR(request))
-               return NULL;
+               return request;
 
        request->mock.delay = delay;
        return request;
-- 
2.47.2