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

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 <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/fcoe/fcoe_ctlr.c b/drivers/scsi/fcoe/fcoe_ctlr.c
index ea23c8dffc252af3d0209167e99118c98575d848..ceb35ebbeb8f14683ce5429be74bced3baec6083 100644 (file)
--- 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);