linux-kernel - [PATCH] scsi: dc395x: fix a missing check on list iterator

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Message-Id: <20220327055921.4191-1-xiam0nd.tong@gmail.com>
Date:   Sun, 27 Mar 2022 13:59:21 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     oliver@...kum.org
Cc:     aliakc@....de, lenehan@...bble.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, dc395x@...bble.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xiaomeng Tong <xiam0nd.tong@...il.com>, stable@...r.kernel.org
Subject: [PATCH] scsi: dc395x: fix a missing check on list iterator

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 a invalid memory access.

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

Cc: stable@...r.kernel.org
Fixes: ^1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
---
 drivers/scsi/dc395x.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/dc395x.c b/drivers/scsi/dc395x.c
index c11916b8ae00..bbc03190a6f2 100644
--- a/drivers/scsi/dc395x.c
+++ b/drivers/scsi/dc395x.c
@@ -3588,10 +3588,19 @@ static struct DeviceCtlBlk *device_alloc(struct AdapterCtlBlk *acb,
 #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,
-- 
2.17.1