sdm660: ADSPRPC: Null check file session ctx during mmap create

During fastrpc mmap create and mmap free, we are dereferencing
file session context without checking for Null.

Change-Id: I65fc2bb566e2e6e7914b86044e17577a96db6b4f
Acked-by: Vishnu Karthik D <vikarthi@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>
diff --git a/drivers/char/adsprpc.c b/drivers/char/adsprpc.c
index 7bc263c..1064e99 100644
--- a/drivers/char/adsprpc.c
+++ b/drivers/char/adsprpc.c
@@ -480,7 +480,7 @@
 
 	if (!IS_ERR_OR_NULL(map->handle))
 		ion_free(fl->apps->client, map->handle);
-	if (sess->smmu.enabled) {
+	if (sess && sess->smmu.enabled) {
 		if (map->size || map->phys)
 			msm_dma_unmap_sg(sess->dev,
 				map->table->sgl,
@@ -558,7 +558,9 @@
 		sess = fl->secsctx;
 	else
 		sess = fl->sctx;
-
+	VERIFY(err, !IS_ERR_OR_NULL(sess));
+	if (err)
+		goto bail;
 	VERIFY(err, !IS_ERR_OR_NULL(map->buf = dma_buf_get(fd)));
 	if (err)
 		goto bail;