drm/amd/amdgpu: ring debugfs is read in increments of 4 bytes

If a user tries to read a non-multiple of 4 bytes it would have
read until the end of the ring potentially crashing the user
task.
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c

@@ -383,7 +383,7 @@ static ssize_t amdgpu_debugfs_ring_read(struct file *f, char __user *buf,
 	int r, i;
 	uint32_t value, result, early[3];
 
-	if (*pos & 3)
+	if (*pos & 3 || size & 3)
 		return -EINVAL;
 
 	result = 0;