netfilter: ipt_recent: fix race between recent_mt_destroy and proc manipulations
The thing is that recent_mt_destroy first flushes the entries
from table with the recent_table_flush and only *after* this
removes the proc file, corresponding to that table.
Thus, if we manage to write to this file the '+XXX' command we
will leak some entries. If we manage to write there a 'clean'
command we'll race in two recent_table_flush flows, since the
recent_mt_destroy calls this outside the recent_lock.
The proper solution as I see it is to remove the proc file first
and then go on with flushing the table. This flushing becomes
safe w/o the lock, since the table is already inaccessible from
the outside.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/netfilter/ipt_recent.c b/net/ipv4/netfilter/ipt_recent.c
index 21cb053..3974d7c 100644
--- a/net/ipv4/netfilter/ipt_recent.c
+++ b/net/ipv4/netfilter/ipt_recent.c
@@ -305,10 +305,10 @@
spin_lock_bh(&recent_lock);
list_del(&t->list);
spin_unlock_bh(&recent_lock);
- recent_table_flush(t);
#ifdef CONFIG_PROC_FS
remove_proc_entry(t->name, proc_dir);
#endif
+ recent_table_flush(t);
kfree(t);
}
mutex_unlock(&recent_mutex);