CVE-2025-39961 Linux内核AMD IOMMU页表级提升竞态条件漏洞

/* * CVE-2025-39961 PoC - Race condition trigger in AMD IOMMU pgtbl * This PoC demonstrates the race condition between increase_address_space() * and fetch_pte() in the AMD IOMMU page table implementation. * * Note: This is a conceptual PoC. Actual exploitation requires kernel-level * access and specific IOMMU configuration. */ #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <unistd.h> #include <sys/mman.h> #define NUM_THREADS 2 #define ITERATIONS 10000 /* Simulated shared page table state */ volatile unsigned long pgtable_root = 0x1000; volatile int pgtable_mode = 3; /* Start with 3-level page table */ volatile int race_detected = 0; /* * Simulates increase_address_space() - CPU 0 (map path) * Updates root first, then mode - creating the race window */ void *cpu0_map_thread(void *arg) { for (int i = 0; i < ITERATIONS; i++) { /* Simulate alloc_pte() -> increase_address_space() */ pgtable_root = 0x2000 + i; /* Update root to new value */ /* Small delay to widen the race window */ for (volatile int j = 0; j < 10; j++); pgtable_mode = 4; /* Update mode after root */ } return NULL; } /* * Simulates iommu_v1_unmap_pages() -> fetch_pte() - CPU 1 (unmap path) * Reads root and mode without lock - detects inconsistency */ void *cpu1_unmap_thread(void *arg) { unsigned long local_root; int local_mode; for (int i = 0; i < ITERATIONS; i++) { local_root = pgtable_root; /* Read root without lock */ local_mode = pgtable_mode; /* Read mode without lock */ /* Check for inconsistency: new root with old mode */ if (local_root >= 0x2000 && local_mode == 3) { race_detected++; fprintf(stderr, "[RACE DETECTED] root=0x%lx mode=%d " "(new root with old mode)\n", local_root, local_mode); } } return NULL; } int main(int argc, char *argv[]) { pthread_t threads[NUM_THREADS]; printf("CVE-2025-39961 PoC: AMD IOMMU pgtbl race condition\n"); printf("Starting %d threads to trigger race...\n", NUM_THREADS); /* Create threads to simulate concurrent map/unmap operations */ pthread_create(&threads[0], NULL, cpu0_map_thread, NULL); pthread_create(&threads[1], NULL, cpu1_unmap_thread, NULL); /* Wait for both threads */ pthread_join(threads[0], NULL); pthread_join(threads[1], NULL); printf("\nResults: %d race conditions detected\n", race_detected); if (race_detected > 0) { printf("Vulnerability confirmed: race condition exists in " "page table level update path\n"); return 1; } printf("No race detected in this run. Try increasing ITERATIONS.\n"); return 0; }