Merge branch 'msm-fixes-4.8' of git://people.freedesktop.org/~robclark/linux into drm-fixes

copy from user fixes.

* 'msm-fixes-4.8' of git://people.freedesktop.org/~robclark/linux:
  drm/msm: protect against faults from copy_from_user() in submit ioctl
  drm/msm: fix use of copy_from_user() while holding spinlock

3 files changed, 40 insertions, 5 deletions

diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index b4bc7f1ef717..d0da52f2a806 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -157,6 +157,12 @@ struct msm_drm_private {
 	struct shrinker shrinker;
 
 	struct msm_vblank_ctrl vblank_ctrl;
+
+	/* task holding struct_mutex.. currently only used in submit path
+	 * to detect and reject faults from copy_from_user() for submit
+	 * ioctl.
+	 */
+	struct task_struct *struct_mutex_task;
 };
 
 struct msm_format {
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 6cd4af443139..85f3047e05ae 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -196,11 +196,20 @@ int msm_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct drm_gem_object *obj = vma->vm_private_data;
 	struct drm_device *dev = obj->dev;
+	struct msm_drm_private *priv = dev->dev_private;
 	struct page **pages;
 	unsigned long pfn;
 	pgoff_t pgoff;
 	int ret;
 
+	/* This should only happen if userspace tries to pass a mmap'd
+	 * but unfaulted gem bo vaddr into submit ioctl, triggering
+	 * a page fault while struct_mutex is already held.  This is
+	 * not a valid use-case so just bail.
+	 */
+	if (priv->struct_mutex_task == current)
+		return VM_FAULT_SIGBUS;
+
 	/* Make sure we don't parallel update on a fault, nor move or remove
 	 * something from beneath our feet
 	 */
diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
index 9766f9ae4b7d..880d6a9af7c8 100644
--- a/drivers/gpu/drm/msm/msm_gem_submit.c
+++ b/drivers/gpu/drm/msm/msm_gem_submit.c
@@ -64,6 +64,14 @@ void msm_gem_submit_free(struct msm_gem_submit *submit)
 	kfree(submit);
 }
 
+static inline unsigned long __must_check
+copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
+{
+	if (access_ok(VERIFY_READ, from, n))
+		return __copy_from_user_inatomic(to, from, n);
+	return -EFAULT;
+}
+
 static int submit_lookup_objects(struct msm_gem_submit *submit,
 		struct drm_msm_gem_submit *args, struct drm_file *file)
 {
@@ -71,6 +79,7 @@ static int submit_lookup_objects(struct msm_gem_submit *submit,
 	int ret = 0;
 
 	spin_lock(&file->table_lock);
+	pagefault_disable();
 
 	for (i = 0; i < args->nr_bos; i++) {
 		struct drm_msm_gem_submit_bo submit_bo;
@@ -84,10 +93,15 @@ static int submit_lookup_objects(struct msm_gem_submit *submit,
 		 */
 		submit->bos[i].flags = 0;
 
-		ret = copy_from_user(&submit_bo, userptr, sizeof(submit_bo));
-		if (ret) {
-			ret = -EFAULT;
-			goto out_unlock;
+		ret = copy_from_user_inatomic(&submit_bo, userptr, sizeof(submit_bo));
+		if (unlikely(ret)) {
+			pagefault_enable();
+			spin_unlock(&file->table_lock);
+			ret = copy_from_user(&submit_bo, userptr, sizeof(submit_bo));
+			if (ret)
+				goto out;
+			spin_lock(&file->table_lock);
+			pagefault_disable();
 		}
 
 		if (submit_bo.flags & ~MSM_SUBMIT_BO_FLAGS) {
@@ -127,9 +141,12 @@ static int submit_lookup_objects(struct msm_gem_submit *submit,
 	}
 
 out_unlock:
-	submit->nr_bos = i;
+	pagefault_enable();
 	spin_unlock(&file->table_lock);
 
+out:
+	submit->nr_bos = i;
+
 	return ret;
 }
 
@@ -377,6 +394,8 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
 	if (ret)
 		return ret;
 
+	priv->struct_mutex_task = current;
+
 	submit = submit_create(dev, gpu, args->nr_bos, args->nr_cmds);
 	if (!submit) {
 		ret = -ENOMEM;
@@ -468,6 +487,7 @@ out:
 	if (ret)
 		msm_gem_submit_free(submit);
 out_unlock:
+	priv->struct_mutex_task = NULL;
 	mutex_unlock(&dev->struct_mutex);
 	return ret;
 }