Commit e3245a7b authored by Pavel Skripkin's avatar Pavel Skripkin Committed by Pablo Neira Ayuso
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netfilter: nft_ct: protect nft_ct_pcpu_template_refcnt with mutex 



Syzbot hit use-after-free in nf_tables_dump_sets. The problem was in
missing lock protection for nft_ct_pcpu_template_refcnt.

Before commit f102d66b ("netfilter: nf_tables: use dedicated
mutex to guard transactions") all transactions were serialized by global
mutex, but then global mutex was changed to local per netnamespace
commit_mutex.

This change causes use-after-free bug, when 2 netnamespaces concurently
changing nft_ct_pcpu_template_refcnt without proper locking. Fix it by
adding nft_ct_pcpu_mutex and protect all nft_ct_pcpu_template_refcnt
changes with it.

Fixes: f102d66b ("netfilter: nf_tables: use dedicated mutex to guard transactions")
Reported-and-tested-by: default avatar <syzbot+649e339fa6658ee623d3@syzkaller.appspotmail.com>
Signed-off-by: default avatarPavel Skripkin <paskripkin@gmail.com>
Acked-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 519133de

net/netfilter/nft_ct.c

+8 −1
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ struct nft_ct_helper_obj { 
#ifdef CONFIG_NF_CONNTRACK_ZONES

static DEFINE_PER_CPU(struct nf_conn *, nft_ct_pcpu_template);

static unsigned int nft_ct_pcpu_template_refcnt __read_mostly;

static DEFINE_MUTEX(nft_ct_pcpu_mutex);

#endif



static u64 nft_ct_get_eval_counter(const struct nf_conn_counter *c,
@@ -525,8 +526,10 @@ static void __nft_ct_set_destroy(const struct nft_ctx *ctx, struct nft_ct *priv) 
#endif

#ifdef CONFIG_NF_CONNTRACK_ZONES

	case NFT_CT_ZONE:

		mutex_lock(&nft_ct_pcpu_mutex);

		if (--nft_ct_pcpu_template_refcnt == 0)

			nft_ct_tmpl_put_pcpu();

		mutex_unlock(&nft_ct_pcpu_mutex);

		break;

#endif

	default:
@@ -564,9 +567,13 @@ static int nft_ct_set_init(const struct nft_ctx *ctx, 
#endif

#ifdef CONFIG_NF_CONNTRACK_ZONES

	case NFT_CT_ZONE:

		if (!nft_ct_tmpl_alloc_pcpu())

		mutex_lock(&nft_ct_pcpu_mutex);

		if (!nft_ct_tmpl_alloc_pcpu()) {

			mutex_unlock(&nft_ct_pcpu_mutex);

			return -ENOMEM;

		}

		nft_ct_pcpu_template_refcnt++;

		mutex_unlock(&nft_ct_pcpu_mutex);

		len = sizeof(u16);

		break;

#endif