Hi, I've got the following error report while fuzzing the kernel with syzkaller.
On commit 926af6273fc683cd98cd0ce7bf0d04a02eed6742. A reproducer and .config are attached kernel BUG at net/core/skbuff.c:105! invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 2 PID: 6558 Comm: syz-executor4 Not tainted 4.10.0-rc7+ #126 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff88003c49c480 task.stack: ffff88003a5c0000 RIP: 0010:skb_panic+0x16f/0x200 net/core/skbuff.c:101 RSP: 0018:ffff88003a5c77d0 EFLAGS: 00010286 RAX: 0000000000000082 RBX: ffff88006be991c0 RCX: 0000000000000000 RDX: 0000000000000082 RSI: ffffffff814567fc RDI: ffffed00074b8eec RBP: ffff88003a5c7838 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000001 R12: ffffffff85231ee0 R13: ffffffff834a6722 R14: 0000000000000003 R15: ffff88006c81c580 FS: 00007f89298c7700(0000) GS:ffff88006de00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020ee5000 CR3: 0000000058697000 CR4: 00000000000006e0 Call Trace: skb_over_panic net/core/skbuff.c:110 [inline] skb_put+0x18d/0x1d0 net/core/skbuff.c:1437 llc_pdu_init_as_xid_cmd include/net/llc_pdu.h:377 [inline] llc_sap_action_send_xid_c+0x2a2/0x3b0 net/llc/llc_s_ac.c:82 llc_exec_sap_trans_actions net/llc/llc_sap.c:152 [inline] llc_sap_next_state net/llc/llc_sap.c:181 [inline] llc_sap_state_process+0x26b/0x4e0 net/llc/llc_sap.c:212 llc_build_and_send_xid_pkt+0x19f/0x200 net/llc/llc_sap.c:276 llc_ui_sendmsg+0xad9/0x1430 net/llc/af_llc.c:938 sock_sendmsg_nosec net/socket.c:635 [inline] sock_sendmsg+0xca/0x110 net/socket.c:645 ___sys_sendmsg+0x9d2/0xae0 net/socket.c:1985 __sys_sendmsg+0x138/0x320 net/socket.c:2019 SYSC_sendmsg net/socket.c:2030 [inline] SyS_sendmsg+0x2d/0x50 net/socket.c:2026 entry_SYSCALL_64_fastpath+0x1f/0xc2 RIP: 0033:0x4458b9 RSP: 002b:00007f89298c6b58 EFLAGS: 00000286 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00000000004458b9 RDX: 0000000000040085 RSI: 0000000020001fc8 RDI: 0000000000000005 RBP: 00000000006e1ae0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000708000 R13: ffffffffffffffff R14: 00000000c0206434 R15: 00000000201fcfe0 Code: 00 00 00 48 89 54 24 10 48 c7 c7 60 19 23 85 48 89 74 24 08 4c 89 04 24 4c 89 ea 4c 89 7c 24 18 45 89 f0 4c 89 e6 e8 1e c0 38 fe <0f> 0b 4c 89 4d b8 4c 89 45 c0 48 89 75 c8 48 89 55 d0 e8 6a 5e RIP: skb_panic+0x16f/0x200 net/core/skbuff.c:101 RSP: ffff88003a5c77d0 ---[ end trace 89f0ca2ea5bc3ead ]--- Kernel panic - not syncing: Fatal exception Dumping ftrace buffer: (ftrace buffer empty) Kernel Offset: disabled Rebooting in 86400 seconds..
.config
Description: Binary data
// autogenerated by syzkaller (http://github.com/google/syzkaller) #ifndef __NR_mmap #define __NR_mmap 9 #endif #ifndef __NR_socket #define __NR_socket 41 #endif #ifndef __NR_sendmsg #define __NR_sendmsg 46 #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 <linux/capability.h> #include <linux/if.h> #include <linux/if_tun.h> #include <linux/kvm.h> #include <linux/sched.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 ? 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; \ } 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); } } 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); } long r[24]; void loop() { memset(r, -1, sizeof(r)); r[0] = execute_syscall(__NR_mmap, 0x20000000ul, 0x851000ul, 0x3ul, 0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0); r[1] = execute_syscall(__NR_socket, 0x1aul, 0x801ul, 0xcb00ul, 0, 0, 0, 0, 0, 0); NONFAILING(*(uint64_t*)0x20001fc8 = (uint64_t)0x20004fa0); NONFAILING(*(uint32_t*)0x20001fd0 = (uint32_t)0x60); NONFAILING(*(uint64_t*)0x20001fd8 = (uint64_t)0x20003000); NONFAILING(*(uint64_t*)0x20001fe0 = (uint64_t)0x1); NONFAILING(*(uint64_t*)0x20001fe8 = (uint64_t)0x20001000); NONFAILING(*(uint64_t*)0x20001ff0 = (uint64_t)0x10); NONFAILING(*(uint32_t*)0x20001ff8 = (uint32_t)0x1); NONFAILING(*(uint16_t*)0x20004fa0 = (uint16_t)0x27); NONFAILING(*(uint32_t*)0x20004fa4 = (uint32_t)0x800); NONFAILING(*(uint32_t*)0x20004fa8 = (uint32_t)0x0); NONFAILING(*(uint32_t*)0x20004fac = (uint32_t)0x0); NONFAILING(*(uint8_t*)0x20004fb0 = (uint8_t)0xfffffffffffffffd); NONFAILING(*(uint8_t*)0x20004fb1 = (uint8_t)0x0); NONFAILING(memcpy( (void*)0x20004fb2, "\x4e\xa6\xf0\xe3\x26\x38\x41\x00\x04\xc3\x84\x5a\xd3\xe8\x12\x92" "\xe2\x97\x1a\x49\xc7\x07\x55\xb5\xa2\x0c\x91\x5b\xe8\xe3\xa2\x1e" "\x49\x17\x62\x02\x27\x36\xcd\x99\x61\x46\xb6\xa2\xa9\x9e\xfe\x01" "\xc9\xcb\xf2\xeb\x94\x94\x94\xc2\x85\x56\x30\xea\x2a\x71\xf9", 63)); NONFAILING(*(uint64_t*)0x20004ff8 = (uint64_t)0x0); NONFAILING(*(uint64_t*)0x20003000 = (uint64_t)0x20002000); NONFAILING(*(uint64_t*)0x20003008 = (uint64_t)0xa7); NONFAILING(memcpy( (void*)0x20002000, "\x95\x45\x2e\xff\xe1\xb2\xde\xa2\x07\xc7\x4b\xbe\x1d\x19\xd1\x1c" "\x25\x40\x57\x3d\x31\xa0\xfa\xc5\xaf\xcc\x44\x1d\x21\xaa\x09\xc4" "\x62\x54\xb9\x46\xcc\x12\x0f\x41\xcc\x99\x90\x8a\x8b\x6e\x1a\x41" "\x27\xfa\x11\xc5\x6c\x68\xdb\xe6\xbc\x4f\x68\x6e\x8b\xe6\xfe\x9e" "\xcd\x87\xd9\x7b\x82\xf9\x0d\x28\x3f\xe7\x2a\x69\xc9\x9d\x38\x7c" "\xcf\x30\x18\xb3\x7a\x2f\xcc\x84\xc2\x0b\x68\x7d\x77\x78\x2a\xd1" "\xe2\x13\xf6\x64\x89\x5e\x8f\x98\xab\x5c\xce\x7f\xfa\xae\x77\x1c" "\x14\x41\xb8\x2d\x30\x3a\x0f\x36\x06\x52\x4f\x9f\xdf\x44\xd8\x32" "\x6b\x28\x91\xde\xa3\x8f\x94\x47\x77\xb0\x1d\xf2\x74\x75\xc5\x53" "\xa4\x1f\x3f\xba\x7b\x0d\x57\xae\xd6\xfb\x0f\xb1\xbb\xfd\x47\x61" "\x36\x7a\x1d\x9e\xda\x18\x48", 167)); NONFAILING(*(uint64_t*)0x20001000 = (uint64_t)0x10); NONFAILING(*(uint32_t*)0x20001008 = (uint32_t)0x1); NONFAILING(*(uint32_t*)0x2000100c = (uint32_t)0x2); r[23] = execute_syscall(__NR_sendmsg, r[1], 0x20001fc8ul, 0x40085ul, 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; }
