CVE-2026-31422 Linux内核cls_flow空指针解引用

/* * PoC for CVE-2026-31422: Linux Kernel cls_flow NULL pointer dereference * Trigger: Create a flow filter on a shared block without a base class. * Compile: gcc -o poc_cve2026_31422 poc_cve2026_31422.c */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <linux/pkt_sched.h> void trigger_vulnerability() { // In a real scenario, this would involve: // 1. Creating a shared block (ingress/egress or qdisc binding). // 2. Sending a netlink message (RTM_NEWTFILTER) with: // - tca[TCA_OPTIONS] pointing to a flow filter. // - Missing tca[TCA_CHAIN] or specific parent handle information // that forces flow_change() to derive baseclass from q->handle. // - The block index must indicate a shared block. printf("Attempting to trigger cls_flow null ptr deref...\n"); // This requires specific netlink message crafting which is omitted for brevity. // The following command sequence mimics the high-level intent: // tc qdisc add dev eth0 ingress // tc filter add dev eth0 parent ffff: protocol ip pref 1 flower ... // (The specific PoC requires setting up a shared block context first) // Hypothetical command line representation if root: // system("tc filter add dev eth0 protocol ip parent ffff: handle ::1 flow ..."); } int main() { trigger_vulnerability(); return 0; }