[PATCH] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

[Tuo Li <islituo@xxxxxxxxx>]

The return value of transport_kmap_data_sg() is assigned to the variable
buf:
  buf = transport_kmap_data_sg(cmd);

And then it is checked:
  if (!buf) {

This indicates that buf can be NULL. However, it is dereferenced in the
following statements:
  if (!(buf[3] & 0x80))
    buf[3] |= 0x80;
  if (!(buf[2] & 0x80))
	buf[2] |= 0x80;

To fix these possible null-pointer dereferences, dereference buf only when
it is not NULL.

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
Signed-off-by: Tuo Li <islituo@xxxxxxxxx>
---
 drivers/target/target_core_pscsi.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 2629d2ef3970..560815729182 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -620,14 +620,14 @@ static void pscsi_complete_cmd(struct se_cmd *cmd, u8 scsi_status,
 			buf = transport_kmap_data_sg(cmd);
 			if (!buf) {
 				; /* XXX: TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE */
-			}
-
-			if (cdb[0] == MODE_SENSE_10) {
-				if (!(buf[3] & 0x80))
-					buf[3] |= 0x80;
 			} else {
-				if (!(buf[2] & 0x80))
-					buf[2] |= 0x80;
+				if (cdb[0] == MODE_SENSE_10) {
+					if (!(buf[3] & 0x80))
+						buf[3] |= 0x80;
+				} else {
+					if (!(buf[2] & 0x80))
+						buf[2] |= 0x80;
+				}
 			}
 
 			transport_kunmap_data_sg(cmd);
-- 
2.25.1