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netfilter: xt_hashlimit: limit the max size of hashtable

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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>
This commit is contained in:
Cong Wang 2020-02-02 20:30:53 -08:00 committed by Pablo Neira Ayuso
parent c4a3922d2d
commit 8d0015a7ab
1 changed files with 10 additions and 0 deletions
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10
net/netfilter/xt_hashlimit.c
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@ -837,6 +837,8 @@ 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,
@ -847,6 +849,14 @@ 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;