[PATCH 5.15 565/667] scsi: dc395x: Fix a missing check on list iterator

[Greg Kroah-Hartman]

From: Xiaomeng Tong <xiam0nd.tong@xxxxxxxxx>

commit 036a45aa587a10fa2abbd50fbd0f6c4cfc44f69f upstream.

The bug is here:

	p->target_id, p->target_lun);

The list iterator 'p' will point to a bogus position containing HEAD if the
list is empty or no element is found. This case must be checked before any
use of the iterator, otherwise it will lead to an invalid memory access.

To fix this bug, add a check. Use a new variable 'iter' as the list
iterator, and use the original variable 'p' as a dedicated pointer to point
to the found element.

Link: https://lore.kernel.org/r/20220414040231.2662-1-xiam0nd.tong@xxxxxxxxx
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@xxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/scsi/dc395x.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

--- a/drivers/scsi/dc395x.c
+++ b/drivers/scsi/dc395x.c
@@ -3590,10 +3590,19 @@ static struct DeviceCtlBlk *device_alloc
 #endif
 	if (dcb->target_lun != 0) {
 		/* Copy settings */
-		struct DeviceCtlBlk *p;
-		list_for_each_entry(p, &acb->dcb_list, list)
-			if (p->target_id == dcb->target_id)
+		struct DeviceCtlBlk *p = NULL, *iter;
+
+		list_for_each_entry(iter, &acb->dcb_list, list)
+			if (iter->target_id == dcb->target_id) {
+				p = iter;
 				break;
+			}
+
+		if (!p) {
+			kfree(dcb);
+			return NULL;
+		}
+
 		dprintkdbg(DBG_1, 
 		       "device_alloc: <%02i-%i> copy from <%02i-%i>\n",
 		       dcb->target_id, dcb->target_lun,