drm/msm/adreno: adreno_gpu: Switch to memdup_user_nul() helper

Use memdup_user_nul() helper instead of open-coding to simplify the code.
Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Reviewed-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/552130/Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/adreno/adreno_gpu.c

@@ -397,17 +397,9 @@ int adreno_set_param(struct msm_gpu *gpu, struct msm_file_private *ctx,
 	case MSM_PARAM_CMDLINE: {
 		char *str, **paramp;
 
-		str = kmalloc(len + 1, GFP_KERNEL);
-		if (!str)
-			return -ENOMEM;
-
-		if (copy_from_user(str, u64_to_user_ptr(value), len)) {
-			kfree(str);
-			return -EFAULT;
-		}
-
-		/* Ensure string is null terminated: */
-		str[len] = '\0';
+		str = memdup_user_nul(u64_to_user_ptr(value), len);
+		if (IS_ERR(str))
+			return PTR_ERR(str);
 
 		mutex_lock(&gpu->lock);