scsi: fcoe: fix use-after-free in fcoe_ctlr_els_send

Johannes Thumshirn · martinkpetersen · commit 2d7d4fd35e6e · 2018-08-02T15:30:03.000-04:00
KASAN reports a use-after-free in fcoe_ctlr_els_send() when we're sending a
LOGO and have FIP debugging enabled. This is because we're first freeing
the skb and then printing the frame's DID. But the DID is a member of the
FC frame header which in turn is the skb's payload.

Exchange the debug print and kfree_skb() calls so we're not touching the
freed data.

Signed-off-by: Johannes Thumshirn &lt;jthumshirn@suse.de&gt;
Reviewed-by: Hannes Reinecke &lt;hare@suse.com&gt;
Signed-off-by: Martin K. Petersen &lt;martin.petersen@oracle.com&gt;
diff --git a/drivers/scsi/fcoe/fcoe_ctlr.c b/drivers/scsi/fcoe/fcoe_ctlr.c
@@ -799,9 +799,9 @@ int fcoe_ctlr_els_send(struct fcoe_ctlr *fip, struct fc_lport *lport,
 	fip->send(fip, skb);
 	return -EINPROGRESS;
 drop:
-	kfree_skb(skb);
 	LIBFCOE_FIP_DBG(fip, "drop els_send op %u d_id %x\n",
 			op, ntoh24(fh->fh_d_id));
+	kfree_skb(skb);
 	return -EINVAL;
 }
 EXPORT_SYMBOL(fcoe_ctlr_els_send);
