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[NEIGH]: Fix race between neigh_parms_release and neightbl_fill_parms

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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>
This commit is contained in:
Pavel Emelyanov 2008-01-10 03:48:38 -08:00 committed by David S. Miller
parent b0de8e402d
commit 9cd4002942
1 changed files with 2 additions and 2 deletions
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4
net/core/neighbour.c
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@ -1316,8 +1316,6 @@ void neigh_parms_release(struct neigh_table *tbl, struct neigh_parms *parms)
*p = parms->next; *p = parms->next;
parms->dead = 1; parms->dead = 1;
write_unlock_bh(&tbl->lock); write_unlock_bh(&tbl->lock);
if (parms->dev)
dev_put(parms->dev);
call_rcu(&parms->rcu_head, neigh_rcu_free_parms); call_rcu(&parms->rcu_head, neigh_rcu_free_parms);
return; 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) void neigh_parms_destroy(struct neigh_parms *parms)
{ {
if (parms->dev)
dev_put(parms->dev);
kfree(parms); kfree(parms);
} }