linux-kernel - [PATCH 1/3] fcoe: fix use-after-free in fcoe_ctlr_els

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Date:   Tue, 31 Jul 2018 15:46:01 +0200
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Linux SCSI Mailinglist <linux-scsi@...r.kernel.org>,
        ard <ard@...ak.net>, Johannes Thumshirn <jthumshirn@...e.de>
Subject: [PATCH 1/3] 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@...e.de>
---
 drivers/scsi/fcoe/fcoe_ctlr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/fcoe/fcoe_ctlr.c b/drivers/scsi/fcoe/fcoe_ctlr.c
index ea23c8dffc25..ceb35ebbeb8f 100644
--- 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);
-- 
2.16.4