Hi, I've got the following error report while running the syzkaller fuzzer:
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: 1 PID: 3933 Comm: syz-executor Not tainted 4.9.0-rc1+ #230 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff88006b79d800 task.stack: ffff88006bbc0000 RIP: 0010:[<ffffffff8120872d>] [<ffffffff8120872d>] __lock_acquire+0x12d/0x3450 kernel/locking/lockdep.c:3221 RSP: 0018:ffff88006bbc7420 EFLAGS: 00010006 RAX: 0000000000000046 RBX: dffffc0000000000 RCX: 0000000000000000 RDX: 000000000000000c RSI: 0000000000000000 RDI: 0000000000000003 RBP: ffff88006bbc75c0 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: ffffffff85f42240 R12: ffff88006b79d800 R13: ffffffff84bfe4e0 R14: 0000000000000001 R15: 0000000000000060 FS: 00007fd9c41cc700(0000) GS:ffff88006cd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000451f80 CR3: 00000000638f0000 CR4: 00000000000006e0 Stack: 0000000000000000 ffff88006bbc0000 ffff88006bbc8000 0000000000000000 0000000000000002 ffff88006b79d800 0000000000000000 ffff88006bbc7f48 ffffffff852adc60 0000000000000000 ffffffff852adc64 1ffffffff0b40135 Call Trace: [<ffffffff8120c5ae>] lock_acquire+0x17e/0x340 kernel/locking/lockdep.c:3746 [< inline >] __mutex_lock_common kernel/locking/mutex.c:521 [<ffffffff83fb6fe1>] mutex_lock_nested+0xb1/0x890 kernel/locking/mutex.c:621 [<ffffffff82db6fd0>] netlink_dump+0x50/0xac0 net/netlink/af_netlink.c:2067 [<ffffffff82dba381>] __netlink_dump_start+0x501/0x770 net/netlink/af_netlink.c:2200 [<ffffffff82dc35b2>] genl_family_rcv_msg+0xa02/0xc80 net/netlink/genetlink.c:595 [<ffffffff82dc39e6>] genl_rcv_msg+0x1b6/0x270 net/netlink/genetlink.c:658 [<ffffffff82dc1a70>] netlink_rcv_skb+0x2c0/0x3b0 net/netlink/af_netlink.c:2281 [<ffffffff82dc2b98>] genl_rcv+0x28/0x40 net/netlink/genetlink.c:669 [< inline >] netlink_unicast_kernel net/netlink/af_netlink.c:1214 [<ffffffff82dc0329>] netlink_unicast+0x5a9/0x880 net/netlink/af_netlink.c:1240 [<ffffffff82dc0fb7>] netlink_sendmsg+0x9b7/0xce0 net/netlink/af_netlink.c:1786 [< inline >] sock_sendmsg_nosec net/socket.c:606 [<ffffffff82b7075c>] sock_sendmsg+0xcc/0x110 net/socket.c:616 [<ffffffff82b709c1>] sock_write_iter+0x221/0x3b0 net/socket.c:814 [< inline >] new_sync_write fs/read_write.c:499 [<ffffffff8151c944>] __vfs_write+0x334/0x570 fs/read_write.c:512 [<ffffffff8152045b>] vfs_write+0x17b/0x500 fs/read_write.c:560 [< inline >] SYSC_write fs/read_write.c:607 [<ffffffff81523d84>] SyS_write+0xd4/0x1a0 fs/read_write.c:599 [<ffffffff83fc0141>] entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:209 Code: 0f 1f 44 00 00 f6 c4 02 0f 85 24 0a 00 00 44 8b 35 c9 61 8b 03 45 85 f6 74 2c 4c 89 fa 48 bb 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 1a 00 0f 85 04 2f 00 00 49 81 3f a0 dc 2a 85 41 be 00 00 RIP [<ffffffff8120872d>] __lock_acquire+0x12d/0x3450 kernel/locking/lockdep.c:3221 RSP <ffff88006bbc7420> ---[ end trace 685b3c182bf7f25c ]--- The reproducer is attached. On commit 1a1891d762d6e64daf07b5be4817e3fbb29e3c59 (Oct 18).
// autogenerated by syzkaller (http://github.com/google/syzkaller) #ifndef __NR_syz_test #define __NR_syz_test 1000001 #endif #ifndef __NR_socket #define __NR_socket 41 #endif #ifndef __NR_write #define __NR_write 1 #endif #ifndef __NR_syz_fuse_mount #define __NR_syz_fuse_mount 1000004 #endif #ifndef __NR_syz_open_dev #define __NR_syz_open_dev 1000002 #endif #ifndef __NR_mmap #define __NR_mmap 9 #endif #ifndef __NR_syz_fuseblk_mount #define __NR_syz_fuseblk_mount 1000005 #endif #ifndef __NR_syz_open_pts #define __NR_syz_open_pts 1000003 #endif #include <fcntl.h> #include <pthread.h> #include <setjmp.h> #include <signal.h> #include <stddef.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/ioctl.h> #include <sys/stat.h> #include <sys/syscall.h> #include <sys/types.h> #include <unistd.h> __thread int skip_segv; __thread jmp_buf segv_env; static void segv_handler(int sig, siginfo_t* info, void* uctx) { if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED)) _longjmp(segv_env, 1); exit(sig); } 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); \ } 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; 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 syz_open_pts(uintptr_t a0, uintptr_t a1) { int ptyno = 0; if (ioctl(a0, TIOCGPTN, &ptyno)) return -1; char buf[128]; sprintf(buf, "/dev/pts/%d", ptyno); return open(buf, a1, 0); } static uintptr_t syz_fuse_mount(uintptr_t a0, uintptr_t a1, uintptr_t a2, uintptr_t a3, uintptr_t a4, uintptr_t a5) { uint64_t target = a0; uint64_t mode = a1; uint64_t uid = a2; uint64_t gid = a3; uint64_t maxread = a4; uint64_t flags = a5; int fd = open("/dev/fuse", O_RDWR); if (fd == -1) return fd; char buf[1024]; sprintf(buf, "fd=%d,user_id=%ld,group_id=%ld,rootmode=0%o", fd, (long)uid, (long)gid, (unsigned)mode & ~3u); if (maxread != 0) sprintf(buf + strlen(buf), ",max_read=%ld", (long)maxread); if (mode & 1) strcat(buf, ",default_permissions"); if (mode & 2) strcat(buf, ",allow_other"); syscall(SYS_mount, "", target, "fuse", flags, buf); return fd; } static uintptr_t syz_fuseblk_mount(uintptr_t a0, uintptr_t a1, uintptr_t a2, uintptr_t a3, uintptr_t a4, uintptr_t a5, uintptr_t a6, uintptr_t a7) { uint64_t target = a0; uint64_t blkdev = a1; uint64_t mode = a2; uint64_t uid = a3; uint64_t gid = a4; uint64_t maxread = a5; uint64_t blksize = a6; uint64_t flags = a7; int fd = open("/dev/fuse", O_RDWR); if (fd == -1) return fd; if (syscall(SYS_mknodat, AT_FDCWD, blkdev, S_IFBLK, makedev(7, 199))) return fd; char buf[256]; sprintf(buf, "fd=%d,user_id=%ld,group_id=%ld,rootmode=0%o", fd, (long)uid, (long)gid, (unsigned)mode & ~3u); if (maxread != 0) sprintf(buf + strlen(buf), ",max_read=%ld", (long)maxread); if (blksize != 0) sprintf(buf + strlen(buf), ",blksize=%ld", (long)blksize); if (mode & 1) strcat(buf, ",default_permissions"); if (mode & 2) strcat(buf, ",allow_other"); syscall(SYS_mount, blkdev, target, "fuseblk", flags, buf); return fd; } 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_test: return 0; case __NR_syz_open_dev: return syz_open_dev(a0, a1, a2); case __NR_syz_open_pts: return syz_open_pts(a0, a1); case __NR_syz_fuse_mount: return syz_fuse_mount(a0, a1, a2, a3, a4, a5); case __NR_syz_fuseblk_mount: return syz_fuseblk_mount(a0, a1, a2, a3, a4, a5, a6, a7); } } long r[4]; int main() { install_segv_handler(); memset(r, -1, sizeof(r)); r[0] = execute_syscall(__NR_mmap, 0x20000000ul, 0x9bc000ul, 0x3ul, 0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0); r[1] = execute_syscall(__NR_socket, 0x10ul, 0x3ul, 0x10ul, 0, 0, 0, 0, 0, 0); NONFAILING(memcpy((void*)0x2061a000, "\x1f\x00\x00\x00\x24\x00\x07\x83\xf9\xff\xff\xff" "\xff\xff\xff\xff\x03\x00\x09\x0a\x45\x58\xe2\x93" "\x3e\x00\x03\x92\x04\x00\x1c\x18\x08\x00\xf3\x01" "\x97\x68\x1a", 39)); r[3] = execute_syscall(__NR_write, r[1], 0x2061a000ul, 0x27ul, 0, 0, 0, 0, 0, 0); return 0; }
