diff mbox series

[net,2/8] netfilter: nft_ct: fix use after free when attaching zone template

Message ID 20220127235235.656931-3-pablo@netfilter.org
State Accepted
Delegated to: Pablo Neira
Headers show
Series [net,1/8] netfilter: Remove flowtable relics | expand

Commit Message

Pablo Neira Ayuso Jan. 27, 2022, 11:52 p.m. UTC 
From: Florian Westphal <fw@strlen.de>

The conversion erroneously removed the refcount increment.
In case we can use the percpu template, we need to increment
the refcount, else it will be released when the skb gets freed.

In case the slowpath is taken, the new template already has a
refcount of 1.

Fixes: 719774377622 ("netfilter: conntrack: convert to refcount_t api")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nft_ct.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
index 518d96c8c247..5adf8bb628a8 100644
--- a/net/netfilter/nft_ct.c
+++ b/net/netfilter/nft_ct.c
@@ -260,9 +260,12 @@  static void nft_ct_set_zone_eval(const struct nft_expr *expr,
 	ct = this_cpu_read(nft_ct_pcpu_template);
 
 	if (likely(refcount_read(&ct->ct_general.use) == 1)) {
+		refcount_inc(&ct->ct_general.use);
 		nf_ct_zone_add(ct, &zone);
 	} else {
-		/* previous skb got queued to userspace */
+		/* previous skb got queued to userspace, allocate temporary
+		 * one until percpu template can be reused.
+		 */
 		ct = nf_ct_tmpl_alloc(nft_net(pkt), &zone, GFP_ATOMIC);
 		if (!ct) {
 			regs->verdict.code = NF_DROP;