netfilter: xt_recent: fix buffer overflow

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>
Cc: stable@kernel.org
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/netfilter/xt_recent.c b/net/netfilter/xt_recent.c
index 132cfaa84cdc..1278f0aa7434 100644
--- a/net/netfilter/xt_recent.c
+++ b/net/netfilter/xt_recent.c
@@ -177,10 +177,10 @@ 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);
 }