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Sat, 07 Mar 2026 09:22:15 -0800 (PST) Received: from v4bel ([58.123.110.97]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c739e170ee4sm4789742a12.21.2026.03.07.09.22.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 07 Mar 2026 09:22:15 -0800 (PST) Date: Sun, 8 Mar 2026 02:22:11 +0900 From: Hyunwoo Kim To: pablo@netfilter.org, fw@strlen.de, phil@nwl.cc, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, imv4bel@gmail.com Subject: [PATCH net] netfilter: ctnetlink: validate CTA_EXPECT_NAT_DIR to prevent OOB access Message-ID: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline ctnetlink_parse_expect_nat() assigns the user-supplied CTA_EXPECT_NAT_DIR value directly to exp->dir without validating that it is within the valid range (0 to IP_CT_DIR_MAX-1). When nf_nat_sip_expected() later uses exp->dir as an index into ct->master->tuplehash[], an out-of-bounds array access occurs. For example, with exp->dir = 100, the access at ct->master->tuplehash[100] reads 5600 bytes past the start of a 320-byte nf_conn object, causing a slab-out-of-bounds read confirmed by UBSAN. Validate exp->dir against IP_CT_DIR_MAX before accepting it. UBSAN report: [ 1.411419] UBSAN: array-index-out-of-bounds in net/netfilter/nf_nat_sip.c:361:31 [ 1.412133] index 100 is out of range for type 'nf_conntrack_tuple_hash [2]' [ 1.412365] CPU: 0 UID: 0 PID: 131 Comm: poc_exp_dir Not tainted 7.0.0-rc2+ #8 PREEMPTLAZY [ 1.412368] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 1.412370] Call Trace: [ 1.412374] [ 1.412375] dump_stack_lvl+0x64/0x80 [ 1.412388] __ubsan_handle_out_of_bounds+0xc9/0x100 [ 1.412398] nf_nat_sip_expected+0x4b9/0x4d0 [ 1.412405] ? __pfx_nf_nat_sip_expected+0x10/0x10 [ 1.412406] ? __asan_memset+0x23/0x50 [ 1.412413] ? nf_ct_ext_add+0x147/0x200 [ 1.412418] init_conntrack.isra.0+0x6c8/0x770 [ 1.412422] ? __pfx_init_conntrack.isra.0+0x10/0x10 [ 1.412424] ? hash_conntrack_raw+0xd9/0x170 [ 1.412425] ? crng_make_state+0x7b/0x180 [ 1.412431] nf_conntrack_in+0x583/0xac0 [ 1.412433] ? __pfx_nf_conntrack_in+0x10/0x10 [ 1.412435] ? __pfx_get_random_u32+0x10/0x10 [ 1.412437] ? __get_random_u32_below+0x16/0x70 [ 1.412439] ? __pfx_ipv4_conntrack_local+0x10/0x10 [ 1.412441] nf_hook_slow+0x75/0x150 [ 1.412444] __ip_local_out+0x20d/0x2f0 [ 1.412449] ? __pfx___ip_local_out+0x10/0x10 [ 1.412451] ? __pfx_dst_output+0x10/0x10 [ 1.412453] ? __pfx_ip_generic_getfrag+0x10/0x10 [ 1.412454] ? __pfx_ip_make_skb+0x10/0x10 [ 1.412456] ip_send_skb+0x31/0xe0 [ 1.412457] udp_send_skb+0x475/0x680 [ 1.412464] udp_sendmsg+0xbe9/0x1150 [ 1.412467] ? __pfx_ip_generic_getfrag+0x10/0x10 [ 1.412468] ? __pfx_udp_sendmsg+0x10/0x10 [ 1.412470] ? __pfx__raw_spin_lock+0x10/0x10 [ 1.412475] ? udp_lib_get_port+0x35b/0xaf0 [ 1.412477] ? __pfx_ip4_datagram_release_cb+0x10/0x10 [ 1.412479] ? __pfx_udp_lib_get_port+0x10/0x10 [ 1.412481] ? __pfx__raw_spin_lock_bh+0x10/0x10 [ 1.412482] ? aa_sk_perm+0x1a0/0x3f0 [ 1.412489] ? __check_object_size+0x4b/0x450 [ 1.412493] ? inet_send_prepare+0x33/0x140 [ 1.412496] __sys_sendto+0x2be/0x2e0 [ 1.412500] ? __pfx___sys_sendto+0x10/0x10 [ 1.412502] ? __pfx_inet_bind_sk+0x10/0x10 [ 1.412504] ? __sys_bind+0x168/0x1a0 [ 1.412506] ? __pfx_ksys_write+0x10/0x10 [ 1.412509] __x64_sys_sendto+0x76/0x90 [ 1.412511] do_syscall_64+0xc7/0x6c0 [ 1.412514] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 1.412521] RIP: 0033:0x423de7 [ 1.412525] Code: c7 c0 ff ff ff ff eb be 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d 7d 12 09 00 00 41 89 ca 74 10 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 69 c3 55 48 89 e5 53 48 83 ec 38 44 89 4d d0 [ 1.412526] RSP: 002b:00007ffeaf8f5098 EFLAGS: 00000202 ORIG_RAX: 000000000000002c [ 1.412531] RAX: ffffffffffffffda RBX: 00007ffeaf8f50c0 RCX: 0000000000423de7 [ 1.412533] RDX: 0000000000000007 RSI: 0000000000488257 RDI: 0000000000000004 [ 1.412534] RBP: 00007ffeaf8f50f0 R08: 00007ffeaf8f50c0 R09: 0000000000000010 [ 1.412535] R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffeaf8f5228 [ 1.412535] R13: 00007ffeaf8f5238 R14: 00000000004af868 R15: 0000000000000001 [ 1.412537] [ 1.412538] ---[ end trace ]--- Fixes: 076a0ca02644 ("netfilter: ctnetlink: add NAT support for expectations") Signed-off-by: Hyunwoo Kim --- net/netfilter/nf_conntrack_netlink.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index c9d725fc2d71..fac75128dfb9 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3497,6 +3497,8 @@ ctnetlink_parse_expect_nat(const struct nlattr *attr, exp->saved_addr = nat_tuple.src.u3; exp->saved_proto = nat_tuple.src.u; exp->dir = ntohl(nla_get_be32(tb[CTA_EXPECT_NAT_DIR])); + if (exp->dir >= IP_CT_DIR_MAX) + return -EINVAL; return 0; #else -- 2.43.0