[PATCH 4.14 078/165] scsi: fcoe: fix use-after-free in fcoe_ctlr_els_send

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johannes Thumshirn <jthumshirn@xxxxxxx>

[ Upstream commit 2d7d4fd35e6e15b47c13c70368da83add19f01e7 ]

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@xxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/scsi/fcoe/fcoe_ctlr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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->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);