[PATCH 4.19 93/97] netfilter: xt_hashlimit: limit the max size of hashtable

Greg Kroah-Hartman
2020-02-27T14:06:32Z

From: Cong Wang <xiyou.wangcong@gmail.com>

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>

---
net/netfilter/xt_hashlimit.c | 10 ++++++++++
1 file changed, 10 insertions(+)

--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -845,6 +845,8 @@ hashlimit_mt(const struct sk_buff *skb,
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(con

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;