From: Pavel Skripkin paskripkin@gmail.com
[ Upstream commit e3245a7b7b34bd2e97f744fd79463add6e9d41f4 ]
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 f102d66b335a ("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: f102d66b335a ("netfilter: nf_tables: use dedicated mutex to guard transactions") Reported-and-tested-by: syzbot+649e339fa6658ee623d3@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin paskripkin@gmail.com Acked-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/netfilter/nft_ct.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c index 7af822a02ce9..7fcb73ac2e6e 100644 --- a/net/netfilter/nft_ct.c +++ b/net/netfilter/nft_ct.c @@ -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, @@ -526,8 +527,10 @@ 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: @@ -565,9 +568,13 @@ 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