[PATCH v3 8/9] drm/amdkfd: Free queue in procfs_queue_type kobject release callback

[Ian Rogers]

struct queue embeds a struct kobject (q->kobj) for procfs entries, but
procfs_queue_type had no .release callback and uninit_queue() freed q
immediately after kfd_procfs_del_queue() called kobject_put(&q->kobj).
With CONFIG_DEBUG_KOBJECT_RELEASE=y, this causes a use-after-free.

Add kfd_procfs_queue_release() to free struct queue from the kobject
release callback, change kfd_procfs_del_queue() to only remove the
kobject from sysfs via kobject_del(), and drop the final reference in
uninit_queue() via kobject_put(). Check q->kobj.state_in_sysfs before
calling kobject_del() in kfd_procfs_del_queue() to avoid warnings if
sysfs creation previously failed.

Fixes: 6d220a7e7971 ("drm/amdkfd: Add queue information to sysfs")
Reviewed-by: Felix Kuehling <felix.kuehling at amd.com>
Signed-off-by: Ian Rogers <irogers at google.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_process.c | 12 +++++++++---
 drivers/gpu/drm/amd/amdkfd/kfd_queue.c   |  5 ++++-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index 6663718fb83c..b349e0d8d47b 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -512,7 +512,15 @@ static const struct sysfs_ops procfs_queue_ops = {
 	.show = kfd_procfs_queue_show,
 };
 
+static void kfd_procfs_queue_release(struct kobject *kobj)
+{
+	struct queue *q = container_of(kobj, struct queue, kobj);
+
+	kfree(q);
+}
+
 static const struct kobj_type procfs_queue_type = {
+	.release = kfd_procfs_queue_release,
 	.sysfs_ops = &procfs_queue_ops,
 	.default_groups = procfs_queue_groups,
 };
@@ -552,7 +560,6 @@ int kfd_procfs_add_queue(struct queue *q)
 	if (ret < 0) {
 		pr_warn("Creating proc/<pid>/queues/%u failed",
 			q->properties.queue_id);
-		kobject_put(&q->kobj);
 		return ret;
 	}
 
@@ -697,11 +704,10 @@ static void kfd_procfs_add_sysfs_files(struct kfd_process *p)
 
 void kfd_procfs_del_queue(struct queue *q)
 {
-	if (!q || !q->process->kobj)
+	if (!q || !q->process || !q->process->kobj || !q->kobj.state_in_sysfs)
 		return;
 
 	kobject_del(&q->kobj);
-	kobject_put(&q->kobj);
 }
 
 int kfd_process_create_wq(void)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_queue.c b/drivers/gpu/drm/amd/amdkfd/kfd_queue.c
index 6010a5d7a7eb..f7413d651620 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_queue.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_queue.c
@@ -83,7 +83,10 @@ int init_queue(struct queue **q, const struct queue_properties *properties)
 
 void uninit_queue(struct queue *q)
 {
-	kfree(q);
+	if (q && q->kobj.state_initialized)
+		kobject_put(&q->kobj);
+	else
+		kfree(q);
 }
 
 #if IS_ENABLED(CONFIG_HSA_AMD_SVM)
-- 
2.56.0.455.g6c5a503b38-goog