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

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 and call
transport_kunmap_data_sg() only when buf is not NULL.

Link: https://lore.kernel.org/r/20210810040414.248167-1-islituo@gmail.com
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Reviewed-by: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Tuo Li <islituo@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 2629d2e..75ef52f 100644 (file)
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -620,17 +620,17 @@ 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);
+                               transport_kunmap_data_sg(cmd);
+                       }
                }
        }
 after_mode_sense: