scsi: 53c700: Check that command slot is not NULL

Add a check for the command slot value to avoid dereferencing a NULL
pointer.

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

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Co-developed-by: Vladimir Telezhnikov <vtelezhnikov@astralinux.ru>
Signed-off-by: Vladimir Telezhnikov <vtelezhnikov@astralinux.ru>
Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>
Link: https://lore.kernel.org/r/20230728123521.18293-1-adiupina@astralinux.ru
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/53c700.c b/drivers/scsi/53c700.c
index e1e4f9d..857be0f 100644 (file)
--- a/drivers/scsi/53c700.c
+++ b/drivers/scsi/53c700.c
@@ -1598,7 +1598,7 @@ NCR_700_intr(int irq, void *dev_id)
                                printk("scsi%d (%d:%d) PHASE MISMATCH IN SEND MESSAGE %d remain, return %p[%04x], phase %s\n", host->host_no, pun, lun, count, (void *)temp, temp - hostdata->pScript, sbcl_to_string(NCR_700_readb(host, SBCL_REG)));
 #endif
                                resume_offset = hostdata->pScript + Ent_SendMessagePhaseMismatch;
-                       } else if(dsp >= to32bit(&slot->pSG[0].ins) &&
+                       } else if (slot && dsp >= to32bit(&slot->pSG[0].ins) &&
                                  dsp <= to32bit(&slot->pSG[NCR_700_SG_SEGMENTS].ins)) {
                                int data_transfer = NCR_700_readl(host, DBC_REG) & 0xffffff;
                                int SGcount = (dsp - to32bit(&slot->pSG[0].ins))/sizeof(struct NCR_700_SG_List);