scsi: dc395x: Fix a missing check on list iterator

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@gmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/scsi/dc395x.c b/drivers/scsi/dc395x.c
index c11916b8ae0013e5036292eef8e71e5e49120d23..bbc03190a6f23d5195d0bf47de32f2e7c35c5cad 100644 (file)
--- 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,