linux-kernel - [PATCH v2] 53c700: add 'slot' check to NULL

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Message-Id: <20230728123521.18293-1-adiupina@astralinux.ru>
Date:   Fri, 28 Jul 2023 15:35:21 +0300
From:   Alexandra Diupina <adiupina@...ralinux.ru>
To:     "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
Cc:     Alexandra Diupina <adiupina@...ralinux.ru>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org,
        Vladimir Telezhnikov <vtelezhnikov@...ralinux.ru>
Subject: [PATCH v2] 53c700: add 'slot' check to NULL

Add a 'slot' check for a null value to avoid
dereferencing the null pointer

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

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Co-developed-by: Vladimir Telezhnikov <vtelezhnikov@...ralinux.ru>
Signed-off-by: Vladimir Telezhnikov <vtelezhnikov@...ralinux.ru>
Signed-off-by: Alexandra Diupina <adiupina@...ralinux.ru>
---
v2: Move the 'slot' variable check to an existing if-else expression
as James E.J. Bottomley <James.Bottomley@...senPartnership.com> suggested
 drivers/scsi/53c700.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/53c700.c b/drivers/scsi/53c700.c
index e1e4f9d10887..857be0f3ae5b 100644
--- 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);
-- 
2.30.2