net: fix geneve_opt length integer overflow

[ Upstream commit b27055a ]

struct geneve_opt uses 5 bit length for each single option, which
means every vary size option should be smaller than 128 bytes.

However, all current related Netlink policies cannot promise this
length condition and the attacker can exploit a exact 128-byte size
option to *fake* a zero length option and confuse the parsing logic,
further achieve heap out-of-bounds read.

One example crash log is like below:

[    3.905425] ==================================================================
[    3.905925] BUG: KASAN: slab-out-of-bounds in nla_put+0xa9/0xe0
[    3.906255] Read of size 124 at addr ffff888005f291cc by task poc/177
[    3.906646]
[    3.906775] CPU: 0 PID: 177 Comm: poc-oob-read Not tainted 6.1.132 #1
[    3.907131] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[    3.907784] Call Trace:
[    3.907925]  <TASK>
[    3.908048]  dump_stack_lvl+0x44/0x5c
[    3.908258]  print_report+0x184/0x4be
[    3.909151]  kasan_report+0xc5/0x100
[    3.909539]  kasan_check_range+0xf3/0x1a0
[    3.909794]  memcpy+0x1f/0x60
[    3.909968]  nla_put+0xa9/0xe0
[    3.910147]  tunnel_key_dump+0x945/0xba0
[    3.911536]  tcf_action_dump_1+0x1c1/0x340
[    3.912436]  tcf_action_dump+0x101/0x180
[    3.912689]  tcf_exts_dump+0x164/0x1e0
[    3.912905]  fw_dump+0x18b/0x2d0
[    3.913483]  tcf_fill_node+0x2ee/0x460
[    3.914778]  tfilter_notify+0xf4/0x180
[    3.915208]  tc_new_tfilter+0xd51/0x10d0
[    3.918615]  rtnetlink_rcv_msg+0x4a2/0x560
[    3.919118]  netlink_rcv_skb+0xcd/0x200
[    3.919787]  netlink_unicast+0x395/0x530
[    3.921032]  netlink_sendmsg+0x3d0/0x6d0
[    3.921987]  __sock_sendmsg+0x99/0xa0
[    3.922220]  __sys_sendto+0x1b7/0x240
[    3.922682]  __x64_sys_sendto+0x72/0x90
[    3.922906]  do_syscall_64+0x5e/0x90
[    3.923814]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[    3.924122] RIP: 0033:0x7e83eab84407
[    3.924331] Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 faf
[    3.925330] RSP: 002b:00007ffff505e370 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
[    3.925752] RAX: ffffffffffffffda RBX: 00007e83eaafa740 RCX: 00007e83eab84407
[    3.926173] RDX: 00000000000001a8 RSI: 00007ffff505e3c0 RDI: 0000000000000003
[    3.926587] RBP: 00007ffff505f460 R08: 00007e83eace1000 R09: 000000000000000c
[    3.926977] R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffff505f3c0
[    3.927367] R13: 00007ffff505f5c8 R14: 00007e83ead1b000 R15: 00005d4fbbe6dcb8

Fix these issues by enforing correct length condition in related
policies.

Fixes: 925d844 ("netfilter: nft_tunnel: add support for geneve opts")
Fixes: 4ece477 ("lwtunnel: add options setting and dumping for geneve")
Fixes: 0ed5269 ("net/sched: add tunnel option support to act_tunnel_key")
Fixes: 0a6e777 ("net/sched: allow flower to match tunnel options")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Link: https://patch.msgid.link/20250402165632.6958-1-linma@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: f0rm2l1n

net/ipv4/ip_tunnel_core.c

@@ -451,7 +451,7 @@ static const struct nla_policy
 geneve_opt_policy[LWTUNNEL_IP_OPT_GENEVE_MAX + 1] = {
 	[LWTUNNEL_IP_OPT_GENEVE_CLASS]	= { .type = NLA_U16 },
 	[LWTUNNEL_IP_OPT_GENEVE_TYPE]	= { .type = NLA_U8 },
-	[LWTUNNEL_IP_OPT_GENEVE_DATA]	= { .type = NLA_BINARY, .len = 128 },
+	[LWTUNNEL_IP_OPT_GENEVE_DATA]	= { .type = NLA_BINARY, .len = 127 },
 };
 
 static const struct nla_policy

net/netfilter/nft_tunnel.c

@@ -335,7 +335,7 @@ static int nft_tunnel_obj_erspan_init(const struct nlattr *attr,
 static const struct nla_policy nft_tunnel_opts_geneve_policy[NFTA_TUNNEL_KEY_GENEVE_MAX + 1] = {
 	[NFTA_TUNNEL_KEY_GENEVE_CLASS]	= { .type = NLA_U16 },
 	[NFTA_TUNNEL_KEY_GENEVE_TYPE]	= { .type = NLA_U8 },
-	[NFTA_TUNNEL_KEY_GENEVE_DATA]	= { .type = NLA_BINARY, .len = 128 },
+	[NFTA_TUNNEL_KEY_GENEVE_DATA]	= { .type = NLA_BINARY, .len = 127 },
 };
 
 static int nft_tunnel_obj_geneve_init(const struct nlattr *attr,

net/sched/act_tunnel_key.c

@@ -68,7 +68,7 @@ geneve_opt_policy[TCA_TUNNEL_KEY_ENC_OPT_GENEVE_MAX + 1] = {
 	[TCA_TUNNEL_KEY_ENC_OPT_GENEVE_CLASS]	   = { .type = NLA_U16 },
 	[TCA_TUNNEL_KEY_ENC_OPT_GENEVE_TYPE]	   = { .type = NLA_U8 },
 	[TCA_TUNNEL_KEY_ENC_OPT_GENEVE_DATA]	   = { .type = NLA_BINARY,
-						       .len = 128 },
+						       .len = 127 },
 };
 
 static const struct nla_policy

net/sched/cls_flower.c

@@ -766,7 +766,7 @@ geneve_opt_policy[TCA_FLOWER_KEY_ENC_OPT_GENEVE_MAX + 1] = {
 	[TCA_FLOWER_KEY_ENC_OPT_GENEVE_CLASS]      = { .type = NLA_U16 },
 	[TCA_FLOWER_KEY_ENC_OPT_GENEVE_TYPE]       = { .type = NLA_U8 },
 	[TCA_FLOWER_KEY_ENC_OPT_GENEVE_DATA]       = { .type = NLA_BINARY,
-						       .len = 128 },
+						       .len = 127 },
 };
 
 static const struct nla_policy