From: Tuan Do Date: Fri, 3 Apr 2026 07:33:17 +0000 (-0700) Subject: netfilter: nft_ct: fix use-after-free in timeout object destroy X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f8dca15a1b190787bbd03285304b569631160eda;p=thirdparty%2Fkernel%2Flinux.git netfilter: nft_ct: fix use-after-free in timeout object destroy nft_ct_timeout_obj_destroy() frees the timeout object with kfree() immediately after nf_ct_untimeout(), without waiting for an RCU grace period. Concurrent packet processing on other CPUs may still hold RCU-protected references to the timeout object obtained via rcu_dereference() in nf_ct_timeout_data(). Add an rcu_head to struct nf_ct_timeout and use kfree_rcu() to defer freeing until after an RCU grace period, matching the approach already used in nfnetlink_cttimeout.c. KASAN report: BUG: KASAN: slab-use-after-free in nf_conntrack_tcp_packet+0x1381/0x29d0 Read of size 4 at addr ffff8881035fe19c by task exploit/80 Call Trace: nf_conntrack_tcp_packet+0x1381/0x29d0 nf_conntrack_in+0x612/0x8b0 nf_hook_slow+0x70/0x100 __ip_local_out+0x1b2/0x210 tcp_sendmsg_locked+0x722/0x1580 __sys_sendto+0x2d8/0x320 Allocated by task 75: nft_ct_timeout_obj_init+0xf6/0x290 nft_obj_init+0x107/0x1b0 nf_tables_newobj+0x680/0x9c0 nfnetlink_rcv_batch+0xc29/0xe00 Freed by task 26: nft_obj_destroy+0x3f/0xa0 nf_tables_trans_destroy_work+0x51c/0x5c0 process_one_work+0x2c4/0x5a0 Fixes: 7e0b2b57f01d ("netfilter: nft_ct: add ct timeout support") Cc: stable@vger.kernel.org Signed-off-by: Tuan Do Signed-off-by: Florian Westphal --- diff --git a/include/net/netfilter/nf_conntrack_timeout.h b/include/net/netfilter/nf_conntrack_timeout.h index 9fdaba911de6..3a66d4abb6d6 100644 --- a/include/net/netfilter/nf_conntrack_timeout.h +++ b/include/net/netfilter/nf_conntrack_timeout.h @@ -14,6 +14,7 @@ struct nf_ct_timeout { __u16 l3num; const struct nf_conntrack_l4proto *l4proto; + struct rcu_head rcu; char data[]; }; diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c index 128ff8155b5d..04c74ccf9b84 100644 --- a/net/netfilter/nft_ct.c +++ b/net/netfilter/nft_ct.c @@ -1020,7 +1020,7 @@ static void nft_ct_timeout_obj_destroy(const struct nft_ctx *ctx, nf_queue_nf_hook_drop(ctx->net); nf_ct_untimeout(ctx->net, timeout); nf_ct_netns_put(ctx->net, ctx->family); - kfree(priv->timeout); + kfree_rcu(priv->timeout, rcu); } static int nft_ct_timeout_obj_dump(struct sk_buff *skb,