linux-kernel - [PATCH 3.16 352/366] ppp: Fix null pointer dereference on registration failure

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Message-ID: <lsq.1539530741.703639721@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org
Subject: [PATCH 3.16 352/366] ppp: Fix null pointer dereference on
 registration failure

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Ben Hutchings <ben@...adent.org.uk>

register_netdevice() will call the device's ndo_uninit operation if
registration fails after it calls the ndo_init operation.  However
ppp_dev_uninit() uses ppp->ppp_net which is currently not set until
after register_netdevice() returns.

This was fixed upstream as part of commit 6d934c70db6e "ppp: add
rtnetlink device creation support".

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -2732,6 +2732,7 @@ static struct ppp *ppp_create_interface(
 
 	ppp = netdev_priv(dev);
 	ppp->dev = dev;
+	ppp->ppp_net = net;
 	ppp->mru = PPP_MRU;
 	init_ppp_file(&ppp->file, INTERFACE);
 	ppp->file.hdrlen = PPP_HDRLEN - 2;	/* don't count proto bytes */
@@ -2801,8 +2802,6 @@ static struct ppp *ppp_create_interface(
 		goto out2;
 	}
 
-	ppp->ppp_net = net;
-
 	atomic_inc(&ppp_unit_count);
 	mutex_unlock(&pn->all_ppp_mutex);
 	rtnl_unlock();