From 9cd40029423701c376391da59d2c6469672b4bed Mon Sep 17 00:00:00 2001
From: Pavel Emelyanov <xemul@openvz.org>
Date: Thu, 10 Jan 2008 03:48:38 -0800
Subject: [NEIGH]: Fix race between neigh_parms_release and neightbl_fill_parms

The neightbl_fill_parms() is called under the write-locked tbl->lock
and accesses the parms->dev. The negh_parm_release() calls the
dev_put(parms->dev) without this lock. This creates a tiny race window
on which the parms contains potentially stale dev pointer.

To fix this race it's enough to move the dev_put() upper under the
tbl->lock, but note, that the parms are held by neighbors and thus can
live after the neigh_parms_release() is called, so we still can have a
parm with bad dev pointer.

I didn't find where the neigh->parms->dev is accessed, but still think
that putting the dev is to be done in a place, where the parms are
really freed. Am I right with that?

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/core/neighbour.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 29b8ee4e35d6..cc8a2f190acf 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1316,8 +1316,6 @@ void neigh_parms_release(struct neigh_table *tbl, struct neigh_parms *parms)
 			*p = parms->next;
 			parms->dead = 1;
 			write_unlock_bh(&tbl->lock);
-			if (parms->dev)
-				dev_put(parms->dev);
 			call_rcu(&parms->rcu_head, neigh_rcu_free_parms);
 			return;
 		}
@@ -1328,6 +1326,8 @@ void neigh_parms_release(struct neigh_table *tbl, struct neigh_parms *parms)
 
 void neigh_parms_destroy(struct neigh_parms *parms)
 {
+	if (parms->dev)
+		dev_put(parms->dev);
 	kfree(parms);
 }
 
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