netfilter: xt_hashlimit: limit the max size of hashtable

commit 8d0015a7ab76b8b1e89a3e5f5710a6e5103f2dd5 upstream.

The user-specified hashtable size is unbound, this could
easily lead to an OOM or a hung task as we hold the global
mutex while allocating and initializing the new hashtable.

Add a max value to cap both cfg->size and cfg->max, as
suggested by Florian.

Reported-and-tested-by: syzbot+adf6c6c2be1c3a718121@syzkaller.appspotmail.com
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index fe8e8a1622b59f3986a1cc65ba569a521b09f762..186f97f1c6c01fa57b0174c9d62d177d756b2fb2 100644 (file)
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -845,6 +845,8 @@ hashlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
        return hashlimit_mt_common(skb, par, hinfo, &info->cfg, 3);
 }
 
+#define HASHLIMIT_MAX_SIZE 1048576
+
 static int hashlimit_mt_check_common(const struct xt_mtchk_param *par,
                                     struct xt_hashlimit_htable **hinfo,
                                     struct hashlimit_cfg3 *cfg,
@@ -855,6 +857,14 @@ static int hashlimit_mt_check_common(const struct xt_mtchk_param *par,
 
        if (cfg->gc_interval == 0 || cfg->expire == 0)
                return -EINVAL;
+       if (cfg->size > HASHLIMIT_MAX_SIZE) {
+               cfg->size = HASHLIMIT_MAX_SIZE;
+               pr_info_ratelimited("size too large, truncated to %u\n", cfg->size);
+       }
+       if (cfg->max > HASHLIMIT_MAX_SIZE) {
+               cfg->max = HASHLIMIT_MAX_SIZE;
+               pr_info_ratelimited("max too large, truncated to %u\n", cfg->max);
+       }
        if (par->family == NFPROTO_IPV4) {
                if (cfg->srcmask > 32 || cfg->dstmask > 32)
                        return -EINVAL;