[PATCH] misc: genwqe: handle a first DMA address of zero

[Yousef Alhouseen]

genwqe_setup_sgl() uses zero as the initial previous DMA address. DMA
address zero is valid, so a first entry at that address enters the
merge path before last_s has been assigned and dereferences NULL.

Only merge adjacent mappings after an SGL data entry has been created.

Signed-off-by: Yousef Alhouseen <alhouseenyousef@xxxxxxxxx>
---
 drivers/misc/genwqe/card_utils.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/genwqe/card_utils.c b/drivers/misc/genwqe/card_utils.c
index a2c4a9b4f871..e3b5fb337182 100644
--- a/drivers/misc/genwqe/card_utils.c
+++ b/drivers/misc/genwqe/card_utils.c
@@ -413,7 +413,7 @@ int genwqe_setup_sgl(struct genwqe_dev *cd, struct genwqe_sgl *sgl,
 			size -= size_to_map;
 			map_offs = 0;
 
-			if (prev_daddr == daddr) {
+			if (last_s && prev_daddr == daddr) {
 				u32 prev_len = be32_to_cpu(last_s->len);
 
 				/* pr_info("daddr combining: "
-- 
2.54.0