Hi, I've got the following error report while fuzzing the kernel with syzkaller. On commit 2868b2513aa732a99ea4a0a6bf10dc93c1f3dac2 (4.11+). A reproducer and .config are attached. kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] SMP KASAN Modules linked in: CPU: 0 PID: 5226 Comm: a.out Not tainted 4.11.0+ #331 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff88006b958000 task.stack: ffff880064328000 RIP: 0010:__free_pages+0x0/0x20 ./include/linux/list.h:92 RSP: 0018:ffff88006432f980 EFLAGS: 00010202 RAX: 0000000000000000 RBX: ffff880066c44358 RCX: 1ffff1000cd88843 RDX: dead4ead00000000 RSI: 0000000000000001 RDI: dead4ead00000000 RBP: ffff88006432f9d8 R08: 1ffff1000c865eca R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000004 R13: 0000000000000020 R14: ffff880066c44200 R15: dffffc0000000000 FS: 00007fc454ac67c0(0000) GS:ffff88006ca00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020002000 CR3: 000000006affa000 CR4: 00000000000006f0 Call Trace: sg_finish_rem_req+0x2a6/0x320 drivers/scsi/sg.c:1839 sg_new_read+0x3c/0x430 drivers/scsi/sg.c:567 sg_read+0x866/0x1830 drivers/scsi/sg.c:455 __vfs_read+0x5c3/0x750 fs/read_write.c:450 vfs_read+0x11e/0x350 fs/read_write.c:473 SYSC_read fs/read_write.c:589 SyS_read+0xfb/0x230 fs/read_write.c:582 entry_SYSCALL_64_fastpath+0x1f/0xbe arch/x86/entry/entry_64.S:204 RIP: 0033:0x7fc4541d9b79 RSP: 002b:00007ffc570f28e8 EFLAGS: 00000297 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007ffc570f2bc0 RCX: 00007fc4541d9b79 RDX: 0000000000000000 RSI: 0000000020002f36 RDI: 0000000000000003 RBP: 00000000004010d0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000000 R13: 00007ffc570f2bc0 R14: 0000000000000000 R15: 0000000000000000 Code: 60 fc ff ff e8 02 35 14 00 4c 8b 95 48 fc ff ff 4c 8b 9d 50 fc ff ff 4c 8b 8d 58 fc ff ff 48 8b 8d 60 fc ff ff e9 73 f9 ff ff 90 <f0> ff 4f 1c 75 16 55 85 f6 48 89 e5 74 07 e8 5d 2f ff ff 5d c3 RIP: __free_pages+0x0/0x20 RSP: ffff88006432f980
Attachment:
.config
Description: Binary data
// autogenerated by syzkaller (http://github.com/google/syzkaller) #ifndef __NR_read #define __NR_read 0 #endif #ifndef __NR_mmap #define __NR_mmap 9 #endif #ifndef __NR_syz_open_dev #define __NR_syz_open_dev 1000002 #endif #ifndef __NR_write #define __NR_write 1 #endif #define _GNU_SOURCE #include <sys/ioctl.h> #include <sys/mman.h> #include <sys/mount.h> #include <sys/prctl.h> #include <sys/resource.h> #include <sys/socket.h> #include <sys/stat.h> #include <sys/syscall.h> #include <sys/time.h> #include <sys/types.h> #include <sys/wait.h> #include <arpa/inet.h> #include <linux/capability.h> #include <linux/if.h> #include <linux/if_ether.h> #include <linux/if_tun.h> #include <linux/ip.h> #include <linux/kvm.h> #include <linux/sched.h> #include <linux/tcp.h> #include <net/if_arp.h> #include <assert.h> #include <dirent.h> #include <errno.h> #include <fcntl.h> #include <grp.h> #include <pthread.h> #include <setjmp.h> #include <signal.h> #include <stdarg.h> #include <stdbool.h> #include <stddef.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> const int kFailStatus = 67; const int kErrorStatus = 68; const int kRetryStatus = 69; __attribute__((noreturn)) void doexit(int status) { volatile unsigned i; syscall(__NR_exit_group, status); for (i = 0;; i++) { } } __attribute__((noreturn)) void fail(const char* msg, ...) { int e = errno; fflush(stdout); va_list args; va_start(args, msg); vfprintf(stderr, msg, args); va_end(args); fprintf(stderr, " (errno %d)\n", e); doexit((e == ENOMEM || e == EAGAIN) ? kRetryStatus : kFailStatus); } __attribute__((noreturn)) void exitf(const char* msg, ...) { int e = errno; fflush(stdout); va_list args; va_start(args, msg); vfprintf(stderr, msg, args); va_end(args); fprintf(stderr, " (errno %d)\n", e); doexit(kRetryStatus); } static int flag_debug; void debug(const char* msg, ...) { if (!flag_debug) return; va_list args; va_start(args, msg); vfprintf(stdout, msg, args); va_end(args); fflush(stdout); } __thread int skip_segv; __thread jmp_buf segv_env; static void segv_handler(int sig, siginfo_t* info, void* uctx) { uintptr_t addr = (uintptr_t)info->si_addr; const uintptr_t prog_start = 1 << 20; const uintptr_t prog_end = 100 << 20; if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED) && (addr < prog_start || addr > prog_end)) { debug("SIGSEGV on %p, skipping\n", addr); _longjmp(segv_env, 1); } debug("SIGSEGV on %p, exiting\n", addr); doexit(sig); for (;;) { } } static void install_segv_handler() { struct sigaction sa; memset(&sa, 0, sizeof(sa)); sa.sa_sigaction = segv_handler; sa.sa_flags = SA_NODEFER | SA_SIGINFO; sigaction(SIGSEGV, &sa, NULL); sigaction(SIGBUS, &sa, NULL); } #define NONFAILING(...) \ { \ __atomic_fetch_add(&skip_segv, 1, __ATOMIC_SEQ_CST); \ if (_setjmp(segv_env) == 0) { \ __VA_ARGS__; \ } \ __atomic_fetch_sub(&skip_segv, 1, __ATOMIC_SEQ_CST); \ } #define BITMASK_LEN(type, bf_len) (type)((1ull << (bf_len)) - 1) #define BITMASK_LEN_OFF(type, bf_off, bf_len) \ (type)(BITMASK_LEN(type, (bf_len)) << (bf_off)) #define STORE_BY_BITMASK(type, addr, val, bf_off, bf_len) \ if ((bf_off) == 0 && (bf_len) == 0) { \ *(type*)(addr) = (type)(val); \ } else { \ type new_val = *(type*)(addr); \ new_val &= ~BITMASK_LEN_OFF(type, (bf_off), (bf_len)); \ new_val |= ((type)(val)&BITMASK_LEN(type, (bf_len))) << (bf_off); \ *(type*)(addr) = new_val; \ } struct csum_inet { uint32_t acc; }; void csum_inet_init(struct csum_inet* csum) { csum->acc = 0; } void csum_inet_update(struct csum_inet* csum, const uint8_t* data, size_t length) { if (length == 0) return; size_t i; for (i = 0; i < length - 1; i += 2) csum->acc += *(uint16_t*)&data[i]; if (length & 1) csum->acc += (uint16_t)data[length - 1]; while (csum->acc > 0xffff) csum->acc = (csum->acc & 0xffff) + (csum->acc >> 16); } uint16_t csum_inet_digest(struct csum_inet* csum) { return ~csum->acc; } static uintptr_t syz_open_dev(uintptr_t a0, uintptr_t a1, uintptr_t a2) { if (a0 == 0xc || a0 == 0xb) { char buf[128]; sprintf(buf, "/dev/%s/%d:%d", a0 == 0xc ? "char" : "block", (uint8_t)a1, (uint8_t)a2); return open(buf, O_RDWR, 0); } else { char buf[1024]; char* hash; NONFAILING(strncpy(buf, (char*)a0, sizeof(buf))); buf[sizeof(buf) - 1] = 0; while ((hash = strchr(buf, '#'))) { *hash = '0' + (char)(a1 % 10); a1 /= 10; } return open(buf, a2, 0); } } static uintptr_t execute_syscall(int nr, uintptr_t a0, uintptr_t a1, uintptr_t a2, uintptr_t a3, uintptr_t a4, uintptr_t a5, uintptr_t a6, uintptr_t a7, uintptr_t a8) { switch (nr) { default: return syscall(nr, a0, a1, a2, a3, a4, a5); case __NR_syz_open_dev: return syz_open_dev(a0, a1, a2); } } static void setup_main_process() { struct sigaction sa; memset(&sa, 0, sizeof(sa)); sa.sa_handler = SIG_IGN; syscall(SYS_rt_sigaction, 0x20, &sa, NULL, 8); syscall(SYS_rt_sigaction, 0x21, &sa, NULL, 8); install_segv_handler(); char tmpdir_template[] = "./syzkaller.XXXXXX"; char* tmpdir = mkdtemp(tmpdir_template); if (!tmpdir) fail("failed to mkdtemp"); if (chmod(tmpdir, 0777)) fail("failed to chmod"); if (chdir(tmpdir)) fail("failed to chdir"); } static void loop(); static void sandbox_common() { prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0); setpgrp(); setsid(); struct rlimit rlim; rlim.rlim_cur = rlim.rlim_max = 128 << 20; setrlimit(RLIMIT_AS, &rlim); rlim.rlim_cur = rlim.rlim_max = 1 << 20; setrlimit(RLIMIT_FSIZE, &rlim); rlim.rlim_cur = rlim.rlim_max = 1 << 20; setrlimit(RLIMIT_STACK, &rlim); rlim.rlim_cur = rlim.rlim_max = 0; setrlimit(RLIMIT_CORE, &rlim); unshare(CLONE_NEWNS); unshare(CLONE_NEWIPC); unshare(CLONE_IO); } static int do_sandbox_none(int executor_pid, bool enable_tun) { int pid = fork(); if (pid) return pid; sandbox_common(); loop(); doexit(1); } static void remove_dir(const char* dir) { DIR* dp; struct dirent* ep; int iter = 0; retry: dp = opendir(dir); if (dp == NULL) { if (errno == EMFILE) { exitf("opendir(%s) failed due to NOFILE, exiting"); } exitf("opendir(%s) failed", dir); } while ((ep = readdir(dp))) { if (strcmp(ep->d_name, ".") == 0 || strcmp(ep->d_name, "..") == 0) continue; char filename[FILENAME_MAX]; snprintf(filename, sizeof(filename), "%s/%s", dir, ep->d_name); struct stat st; if (lstat(filename, &st)) exitf("lstat(%s) failed", filename); if (S_ISDIR(st.st_mode)) { remove_dir(filename); continue; } int i; for (i = 0;; i++) { debug("unlink(%s)\n", filename); if (unlink(filename) == 0) break; if (errno == EROFS) { debug("ignoring EROFS\n"); break; } if (errno != EBUSY || i > 100) exitf("unlink(%s) failed", filename); debug("umount(%s)\n", filename); if (umount2(filename, MNT_DETACH)) exitf("umount(%s) failed", filename); } } closedir(dp); int i; for (i = 0;; i++) { debug("rmdir(%s)\n", dir); if (rmdir(dir) == 0) break; if (i < 100) { if (errno == EROFS) { debug("ignoring EROFS\n"); break; } if (errno == EBUSY) { debug("umount(%s)\n", dir); if (umount2(dir, MNT_DETACH)) exitf("umount(%s) failed", dir); continue; } if (errno == ENOTEMPTY) { if (iter < 100) { iter++; goto retry; } } } exitf("rmdir(%s) failed", dir); } } static uint64_t current_time_ms() { struct timespec ts; if (clock_gettime(CLOCK_MONOTONIC, &ts)) fail("clock_gettime failed"); return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000; } static void test(); void loop() { int iter; for (iter = 0;; iter++) { char cwdbuf[256]; sprintf(cwdbuf, "./%d", iter); if (mkdir(cwdbuf, 0777)) fail("failed to mkdir"); int pid = fork(); if (pid < 0) fail("clone failed"); if (pid == 0) { prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0); setpgrp(); if (chdir(cwdbuf)) fail("failed to chdir"); test(); doexit(0); } int status = 0; uint64_t start = current_time_ms(); for (;;) { int res = waitpid(-1, &status, __WALL | WNOHANG); if (res == pid) break; usleep(1000); if (current_time_ms() - start > 5 * 1000) { kill(-pid, SIGKILL); kill(pid, SIGKILL); while (waitpid(-1, &status, __WALL) != pid) { } break; } } remove_dir(cwdbuf); } } long r[15]; void test() { memset(r, -1, sizeof(r)); r[0] = execute_syscall(__NR_mmap, 0x20000000ul, 0x5000ul, 0x3ul, 0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0); NONFAILING(memcpy((void*)0x20000000, "\x2f\x64\x65\x76\x2f\x73\x67\x23\x00", 9)); r[2] = execute_syscall(__NR_syz_open_dev, 0x20000000ul, 0x0ul, 0x2ul, 0, 0, 0, 0, 0, 0); NONFAILING(*(uint64_t*)0x20001fdc = (uint64_t)0x0); NONFAILING(*(uint64_t*)0x20001fe4 = (uint64_t)0x0); NONFAILING(*(uint16_t*)0x20001fec = (uint16_t)0x3); NONFAILING(*(uint16_t*)0x20001fee = (uint16_t)0x4); NONFAILING(*(uint32_t*)0x20001ff0 = (uint32_t)0x9); NONFAILING(*(uint64_t*)0x20001ff4 = (uint64_t)0x0); NONFAILING(*(uint64_t*)0x20001ffc = (uint64_t)0x2710); NONFAILING(*(uint16_t*)0x20002004 = (uint16_t)0x7); NONFAILING(*(uint16_t*)0x20002006 = (uint16_t)0x7); NONFAILING(*(uint32_t*)0x20002008 = (uint32_t)0x8); r[13] = execute_syscall(__NR_write, r[2], 0x20001fdcul, 0x30ul, 0, 0, 0, 0, 0, 0); r[14] = execute_syscall(__NR_read, r[2], 0x20002f36ul, 0x0ul, 0, 0, 0, 0, 0, 0); } int main() { setup_main_process(); int pid = do_sandbox_none(0, false); int status = 0; while (waitpid(pid, &status, __WALL) != pid) { } return 0; }
