netfilter: ipt_CLUSTERIP: fix out-of-bounds accesses in clusterip_tg_check()

Commit 136e92bbec0a switched local_nodes from an array to a bitmask
but did not add proper bounds checks. As the result
clusterip_config_init_nodelist() can both over-read
ipt_clusterip_tgt_info.local_nodes and over-write
clusterip_config.local_nodes.

Add bounds checks for both.

Fixes: 136e92bbec0a ("[NETFILTER] CLUSTERIP: use a bitmap to store node responsibility data")
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 13 insertions, 3 deletions

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 69060e3abe85..1e4a7209a3d2 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -431,7 +431,7 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
         struct ipt_clusterip_tgt_info *cipinfo = par->targinfo;
         const struct ipt_entry *e = par->entryinfo;
         struct clusterip_config *config;
-        int ret;
+        int ret, i;
 
         if (par->nft_compat) {
                 pr_err("cannot use CLUSTERIP target from nftables compat\n");
@@ -450,8 +450,18 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
                 pr_info("Please specify destination IP\n");
                 return -EINVAL;
         }
-
-        /* FIXME: further sanity checks */
+        if (cipinfo->num_local_nodes > ARRAY_SIZE(cipinfo->local_nodes)) {
+                pr_info("bad num_local_nodes %u\n", cipinfo->num_local_nodes);
+                return -EINVAL;
+        }
+        for (i = 0; i < cipinfo->num_local_nodes; i++) {
+                if (cipinfo->local_nodes[i] - 1 >=
+                    sizeof(config->local_nodes) * 8) {
+                        pr_info("bad local_nodes[%d] %u\n",
+                                i, cipinfo->local_nodes[i]);
+                        return -EINVAL;
+                }
+        }
 
         config = clusterip_config_find_get(par->net, e->ip.dst.s_addr, 1);
         if (!config) {