[PATCH 6.1 v2 1/3] scsi: aic79xx: check for non-NULL scb in ahd_handle_seqint

[Boris Belyavtsev <bbelyavtsev@usergate.com>]

NULL pointer dereference is possible when compiled with AHD_DEBUG and
AHD_SHOW_RECOVERY is set if data in SCBPTR и SCBPTR+1 ports is
incorrect.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Boris Belyavtsev <bbelyavtsev@usergate.com>
---
 drivers/scsi/aic7xxx/aic79xx_core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/aic7xxx/aic79xx_core.c b/drivers/scsi/aic7xxx/aic79xx_core.c
index f9372a81cd4e..a4d5376123d3 100644
--- a/drivers/scsi/aic7xxx/aic79xx_core.c
+++ b/drivers/scsi/aic7xxx/aic79xx_core.c
@@ -2205,13 +2205,16 @@ ahd_handle_seqint(struct ahd_softc *ahd, u_int intstat)
 			ahd_print_path(ahd, scb);
 			printk("data overrun detected %s.  Tag == 0x%x.\n",
 			       ahd_lookup_phase_entry(lastphase)->phasemsg,
-			       SCB_GET_TAG(scb));
+			       scb != NULL ? SCB_GET_TAG(scb) : 0);
 			ahd_print_path(ahd, scb);
 			printk("%s seen Data Phase.  Length = %ld.  "
 			       "NumSGs = %d.\n",
 			       ahd_inb(ahd, SEQ_FLAGS) & DPHASE
 			       ? "Have" : "Haven't",
-			       ahd_get_transfer_length(scb), scb->sg_count);
+			       scb != NULL ? ahd_get_transfer_length(scb) : -1,
+			       scb != NULL ? scb->sg_count : -1);
+			if (scb == NULL)
+				break;
 			ahd_dump_sglist(scb);
 		}
 #endif
-- 
2.43.0