Hi, I think I found a reproducible kernel bug in version 5.0.4. Source file: arch/x86/kernel/unwind_orc.c:505 The KASAN output is as following: [ 26.095365] BUG: KASAN: stack-out-of-bounds in unwind_next_frame+0x1403/0x19e0 [ 26.095365] Read of size 8 at addr ffff88805cc67d18 by task syz-executor.0/2296 [ 26.095365] [ 26.098418] CPU: 0 PID: 2296 Comm: syz-executor.0 Not tainted 5.0.4 #1 [ 26.098418] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 26.098418] Call Trace: [ 26.098418] dump_stack+0xca/0x13e [ 26.098418] ? unwind_next_frame+0x1403/0x19e0 [ 26.098418] print_address_description+0x67/0x237 [ 26.098418] ? unwind_next_frame+0x1403/0x19e0 [ 26.098418] ? unwind_next_frame+0x1403/0x19e0 [ 26.098418] kasan_report.cold.3+0x1a/0x3b [ 26.098418] ? error_entry+0x40/0xf0 [ 26.098418] ? unwind_next_frame+0x1403/0x19e0 [ 26.098418] unwind_next_frame+0x1403/0x19e0 [ 26.098418] ? retint_kernel+0x10/0x10 [ 26.098418] ? deref_stack_reg+0xe0/0xe0 [ 26.098418] ? retint_kernel+0x10/0x10 [ 26.098418] perf_callchain_kernel+0x400/0x5b0 [ 26.098418] ? arch_perf_update_userpage+0x370/0x370 [ 26.110600] ? put_callchain_buffers+0x70/0x70 [ 26.110600] get_perf_callchain+0x370/0x800 [ 26.110600] ? put_callchain_buffers+0x70/0x70 [ 26.110600] ? perf_callchain+0x171/0x1c0 [ 26.110600] perf_callchain+0x163/0x1c0 [ 26.110600] perf_prepare_sample+0x88d/0x15a0 [ 26.115655] ? perf_callchain+0x1c0/0x1c0 [ 26.115655] ? perf_prepare_sample+0x15a0/0x15a0 [ 26.115655] ? perf_event_output_forward+0x1bf/0x2a0 [ 26.115655] perf_event_output_forward+0x108/0x2a0 [ 26.115655] ? perf_prepare_sample+0x15a0/0x15a0 [ 26.115655] ? __perf_event_overflow+0x1e7/0x360 [ 26.115655] ? perf_swevent_overflow+0x8d/0x140 [ 26.115655] __perf_event_overflow+0x13f/0x360 [ 26.115655] perf_swevent_overflow+0xa7/0x140 [ 26.115655] perf_swevent_event+0x14d/0x2e0 [ 26.115655] perf_tp_event+0x26a/0x880 [ 26.115655] ? perf_swevent_event+0x2e0/0x2e0 [ 26.115655] ? perf_pmu_nop_int+0x5/0x10 [ 26.115655] ? group_sched_in+0x177/0x3f0 [ 26.115655] ? flexible_sched_in+0xbc/0x5f0 [ 26.115655] ? __lock_acquire+0x5d6/0x4630 [ 26.115655] ? perf_trace_run_bpf_submit+0x112/0x1b0 [ 26.115655] ? perf_trace_run_bpf_submit+0x112/0x1b0 [ 26.115655] perf_trace_run_bpf_submit+0x112/0x1b0 [ 26.115655] ? memset+0x1f/0x40 [ 26.115655] perf_trace_lock_acquire+0x374/0x630 [ 26.115655] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 26.115655] ? perf_trace_lock+0x520/0x520 [ 26.115655] ? retint_kernel+0x10/0x10 [ 26.115655] lock_acquire+0x1ed/0x2e0 [ 26.115655] ? posix_ktime_get_ts+0x11/0x20 [ 26.115655] ktime_get_ts64+0x187/0x2e0 [ 26.115655] ? posix_ktime_get_ts+0x11/0x20 [ 26.115655] ? __x64_sys_futex+0x35b/0x4e0 [ 26.115655] posix_ktime_get_ts+0x11/0x20 [ 26.115655] __x64_sys_clock_gettime+0x152/0x240 [ 26.115655] ? __x64_sys_timer_create+0x1b0/0x1b0 [ 26.115655] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 26.115655] ? trace_hardirqs_off_caller+0x55/0x1c0 [ 26.115655] ? do_syscall_64+0x1a/0x4e0 [ 26.115655] do_syscall_64+0xbc/0x4e0 [ 26.115655] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 26.115655] RIP: 0033:0x45b37a [ 26.115655] Code: 31 f6 31 ff e8 27 fe ff ff b8 40 6b a4 00 48 83 c4 08 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 63 ff b8 e4 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 02 f3 c3 48 c7 c2 d4 ff ff ff f7 d8 64 89 02 [ 26.115655] RSP: 002b:00007f2d0f4d3c78 EFLAGS: 00000202 ORIG_RAX: 00000000000000e4 [ 26.115655] RAX: ffffffffffffffda RBX: 000000000072bf00 RCX: 000000000045b37a [ 26.115655] RDX: 00000000004b587f RSI: 00007f2d0f4d3c80 RDI: 0000000000000001 [ 26.115655] RBP: 0000000000000000 R08: 0000000000000000 R09: 00007f2d0f4d4700 [ 26.115655] R10: 0000000000000003 R11: 0000000000000202 R12: 00000000004b587f [ 26.115655] R13: 00000000004c9050 R14: 00007f2d0f4d49c0 R15: 00007f2d0f4d4700 [ 26.115655] [ 26.115655] The buggy address belongs to the page: [ 26.115655] page:ffffea00017319c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0 [ 26.115655] flags: 0x100000000000000() [ 26.115655] raw: 0100000000000000 ffffea00017319c8 ffffea00017319c8 0000000000000000 [ 26.115655] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 [ 26.115655] page dumped because: kasan: bad access detected [ 26.115655] [ 26.115655] Memory state around the buggy address: [ 26.115655] ffff88805cc67c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 26.115655] ffff88805cc67c80: 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 04 [ 26.115655] >ffff88805cc67d00: f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 00 00 00 00 00 [ 26.115655] ^ [ 26.115655] ffff88805cc67d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 26.115655] ffff88805cc67e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
And the c reproducer is: #define _GNU_SOURCE #include <dirent.h> #include <endian.h> #include <errno.h> #include <fcntl.h> #include <pthread.h> #include <signal.h> #include <stdarg.h> #include <stdbool.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/prctl.h> #include <sys/stat.h> #include <sys/syscall.h> #include <sys/types.h> #include <sys/wait.h> #include <time.h> #include <unistd.h> #include <linux/futex.h> static void sleep_ms(uint64_t ms) { usleep(ms * 1000); } static uint64_t current_time_ms(void) { struct timespec ts; if (clock_gettime(CLOCK_MONOTONIC, &ts)) exit(1); return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000; } static void thread_start(void* (*fn)(void*), void* arg) { pthread_t th; pthread_attr_t attr; pthread_attr_init(&attr); pthread_attr_setstacksize(&attr, 128 << 10); int i; for (i = 0; i < 100; i++) { if (pthread_create(&th, &attr, fn, arg) == 0) { pthread_attr_destroy(&attr); return; } if (errno == EAGAIN) { usleep(50); continue; } break; } exit(1); } #define BITMASK(bf_off,bf_len) (((1ull << (bf_len)) - 1) << (bf_off)) #define STORE_BY_BITMASK(type,htobe,addr,val,bf_off,bf_len) *(type*)(addr) = htobe((htobe(*(type*)(addr)) & ~BITMASK((bf_off), (bf_len))) | (((type)(val) << (bf_off)) & BITMASK((bf_off), (bf_len)))) typedef struct { int state; } event_t; static void event_init(event_t* ev) { ev->state = 0; } static void event_reset(event_t* ev) { ev->state = 0; } static void event_set(event_t* ev) { if (ev->state) exit(1); __atomic_store_n(&ev->state, 1, __ATOMIC_RELEASE); syscall(SYS_futex, &ev->state, FUTEX_WAKE | FUTEX_PRIVATE_FLAG); } static void event_wait(event_t* ev) { while (!__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE)) syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, 0); } static int event_isset(event_t* ev) { return __atomic_load_n(&ev->state, __ATOMIC_ACQUIRE); } static int event_timedwait(event_t* ev, uint64_t timeout) { uint64_t start = current_time_ms(); uint64_t now = start; for (;;) { uint64_t remain = timeout - (now - start); struct timespec ts; ts.tv_sec = remain / 1000; ts.tv_nsec = (remain % 1000) * 1000 * 1000; syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, &ts); if (__atomic_load_n(&ev->state, __ATOMIC_RELAXED)) return 1; now = current_time_ms(); if (now - start > timeout) return 0; } } static bool write_file(const char* file, const char* what, ...) { char buf[1024]; va_list args; va_start(args, what); vsnprintf(buf, sizeof(buf), what, args); va_end(args); buf[sizeof(buf) - 1] = 0; int len = strlen(buf); int fd = open(file, O_WRONLY | O_CLOEXEC); if (fd == -1) return false; if (write(fd, buf, len) != len) { int err = errno; close(fd); errno = err; return false; } close(fd); return true; } static void kill_and_wait(int pid, int* status) { kill(-pid, SIGKILL); kill(pid, SIGKILL); int i; for (i = 0; i < 100; i++) { if (waitpid(-1, status, WNOHANG | __WALL) == pid) return; usleep(1000); } DIR* dir = opendir("/sys/fs/fuse/connections"); if (dir) { for (;;) { struct dirent* ent = readdir(dir); if (!ent) break; if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0) continue; char abort[300]; snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort", ent->d_name); int fd = open(abort, O_WRONLY); if (fd == -1) { continue; } if (write(fd, abort, 1) < 0) { } close(fd); } closedir(dir); } else { } while (waitpid(-1, status, __WALL) != pid) { } } #define SYZ_HAVE_SETUP_TEST 1 static void setup_test() { prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0); setpgrp(); write_file("/proc/self/oom_score_adj", "1000"); } #define SYZ_HAVE_RESET_TEST 1 static void reset_test() { int fd; for (fd = 3; fd < 30; fd++) close(fd); } struct thread_t { int created, call; event_t ready, done; }; static struct thread_t threads[16]; static void execute_call(int call); static int running; static void* thr(void* arg) { struct thread_t* th = (struct thread_t*)arg; for (;;) { event_wait(&th->ready); event_reset(&th->ready); execute_call(th->call); __atomic_fetch_sub(&running, 1, __ATOMIC_RELAXED); event_set(&th->done); } return 0; } static void execute_one(void) { int i, call, thread; int collide = 0; again: for (call = 0; call < 1; call++) { for (thread = 0; thread < (int)(sizeof(threads) / sizeof(threads[0])); thread++) { struct thread_t* th = &threads[thread]; if (!th->created) { th->created = 1; event_init(&th->ready); event_init(&th->done); event_set(&th->done); thread_start(thr, th); } if (!event_isset(&th->done)) continue; event_reset(&th->done); th->call = call; __atomic_fetch_add(&running, 1, __ATOMIC_RELAXED); event_set(&th->ready); if (collide && (call % 2) == 0) break; event_timedwait(&th->done, 45); break; } } for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++) sleep_ms(1); if (!collide) { collide = 1; goto again; } } static void execute_one(void); #define WAIT_FLAGS __WALL static void loop(void) { int iter; for (iter = 0;; iter++) { int pid = fork(); if (pid < 0) exit(1); if (pid == 0) { setup_test(); execute_one(); reset_test(); exit(0); } int status = 0; uint64_t start = current_time_ms(); for (;;) { if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid) break; sleep_ms(1); if (current_time_ms() - start < 5 * 1000) continue; kill_and_wait(pid, &status); break; } } } void execute_call(int call) { switch (call) { case 0: *(uint32_t*)0x20000040 = 2; *(uint32_t*)0x20000044 = 0x70; *(uint8_t*)0x20000048 = 0x74; *(uint8_t*)0x20000049 = 0; *(uint8_t*)0x2000004a = 0; *(uint8_t*)0x2000004b = 0; *(uint32_t*)0x2000004c = 0; *(uint64_t*)0x20000050 = 3; *(uint64_t*)0x20000058 = 0x20; *(uint64_t*)0x20000060 = 0; STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 0, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 1, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 2, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 3, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 4, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 5, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 6, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 7, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 8, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 9, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 10, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 11, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 12, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 13, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 14, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 15, 2); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 17, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 18, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 19, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 20, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 21, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 22, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 23, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 24, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 25, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 26, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 27, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 28, 1); STORE_BY_BITMASK(uint64_t, , 0x20000068, 0, 29, 35); *(uint32_t*)0x20000070 = 0; *(uint32_t*)0x20000074 = 0; *(uint64_t*)0x20000078 = 0; *(uint64_t*)0x20000080 = 0; *(uint64_t*)0x20000088 = 0; *(uint64_t*)0x20000090 = 0; *(uint32_t*)0x20000098 = 0; *(uint32_t*)0x2000009c = 0; *(uint64_t*)0x200000a0 = 0; *(uint32_t*)0x200000a8 = 0; *(uint16_t*)0x200000ac = 0; *(uint16_t*)0x200000ae = 0; syscall(__NR_perf_event_open, 0x20000040, 0, 0, -1, 0); break; } } int main(void) { syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0); loop(); return 0; } Looking forward to your reply Alex