netfilter: xt_recent: fix buffer overflow

commit 2c08522e5d2f0af2d6f05be558946dcbf8173683 upstream.

e->index overflows e->stamps[] every ip_pkt_list_tot packets.

Consider the case when ip_pkt_list_tot==1; the first packet received is stored
in e->stamps[0] and e->index is initialized to 1. The next received packet
timestamp is then stored at e->stamps[1] in recent_entry_update(),
a buffer overflow because the maximum e->stamps[] index is 0.

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/netfilter/xt_recent.c b/net/netfilter/xt_recent.c
index eb0ceb8465270d355d44842b1b82e91e41b6830e..d940a6367c7a8ced424d8c042d81c2f908dbb20d 100644 (file)
--- a/net/netfilter/xt_recent.c
+++ b/net/netfilter/xt_recent.c
@@ -173,10 +173,10 @@ recent_entry_init(struct recent_table *t, const union nf_inet_addr *addr,
 
 static void recent_entry_update(struct recent_table *t, struct recent_entry *e)
 {
+       e->index %= ip_pkt_list_tot;
        e->stamps[e->index++] = jiffies;
        if (e->index > e->nstamps)
                e->nstamps = e->index;
-       e->index %= ip_pkt_list_tot;
        list_move_tail(&e->lru_list, &t->lru_list);
 }