Hi, I've got the following error report while fuzzing the kernel with syzkaller.
A reproducer is attached. On commit 9c763584b7c8911106bb77af7e648bef09af9d80 (4.9-rc6, Nov 20). ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:3029! invalid opcode: 0000 [#1] SMP KASAN Modules linked in: CPU: 1 PID: 3854 Comm: a.out Not tainted 4.9.0-rc6+ #431 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff880068472c00 task.stack: ffff880063ec8000 RIP: 0010:[<ffffffff82b8fd85>] [<ffffffff82b8fd85>] skb_pull_rcsum+0x255/0x350 net/core/skbuff.c:3029 RSP: 0018:ffff880063ecf660 EFLAGS: 00010297 RAX: ffff880068472c00 RBX: ffff880065a2da00 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 000000000000000d RDI: ffffed000c7d9ec0 RBP: ffff880063ecf690 R08: 1ffff1000d08e67e R09: 1ffff1000cb45b50 R10: dffffc0000000000 R11: 0000000000000000 R12: ffff880065a2da80 R13: 0000000000000008 R14: ffff880065a2dad8 R15: 0000000000000001 FS: 00007fbb006497c0(0000) GS:ffff88006cd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020032fe0 CR3: 00000000636d9000 CR4: 00000000000006e0 Stack: ffff88006bfbb948 ffff880065a2da00 ffff880064160000 1ffff1000cb45b52 0000000000000000 1ffff1000d4d3933 ffff880063ecf6f8 ffffffff83354ced 00000000fffffe00 ffff880065a2da90 ffff880063ecf6c0 ffffffff00000001 Call Trace: [< inline >] udp_csum_pull_header ./include/net/udp.h:166 [<ffffffff83354ced>] udpv6_queue_rcv_skb+0x37d/0x17b0 net/ipv6/udp.c:625 [< inline >] sk_backlog_rcv ./include/net/sock.h:874 [<ffffffff82b7eec6>] __release_sock+0x126/0x3a0 net/core/sock.c:2046 [<ffffffff82b7f199>] release_sock+0x59/0x1c0 net/core/sock.c:2504 [<ffffffff8334fc50>] udpv6_sendmsg+0x1310/0x24a0 net/ipv6/udp.c:1273 [<ffffffff83174fa7>] inet_sendmsg+0x317/0x4e0 net/ipv4/af_inet.c:734 [< inline >] sock_sendmsg_nosec net/socket.c:621 [<ffffffff82b7176c>] sock_sendmsg+0xcc/0x110 net/socket.c:631 [<ffffffff82b719d1>] sock_write_iter+0x221/0x3b0 net/socket.c:829 [<ffffffff8151e69b>] do_iter_readv_writev+0x2bb/0x3f0 fs/read_write.c:695 [<ffffffff81520501>] do_readv_writev+0x431/0x730 fs/read_write.c:872 [<ffffffff81520d2f>] vfs_writev+0x8f/0xc0 fs/read_write.c:911 [<ffffffff81520e41>] do_writev+0xe1/0x240 fs/read_write.c:944 [< inline >] SYSC_writev fs/read_write.c:1017 [<ffffffff81523ca7>] SyS_writev+0x27/0x30 fs/read_write.c:1014 [<ffffffff83fc4381>] entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:209 Code: 89 f8 49 c1 e8 03 47 0f b6 14 08 45 84 d2 74 0a 41 80 fa 03 0f 8e cf 00 00 00 80 a3 91 00 00 00 f9 e9 43 ff ff ff e8 3b 79 79 fe <0f> 0b e8 34 79 79 fe 0f 0b e8 2d 79 79 fe 48 8b 7d d0 31 d2 44 RIP [<ffffffff82b8fd85>] skb_pull_rcsum+0x255/0x350 net/core/skbuff.c:3029 RSP <ffff880063ecf660> ---[ end trace a5d5d2cef6a25ecb ]--- ==================================================================
// autogenerated by syzkaller (http://github.com/google/syzkaller) #ifndef __NR_mmap #define __NR_mmap 9 #endif #ifndef __NR_bind #define __NR_bind 49 #endif #ifndef __NR_sendmsg #define __NR_sendmsg 46 #endif #ifndef __NR_writev #define __NR_writev 20 #endif #ifndef __NR_socket #define __NR_socket 41 #endif #ifndef __NR_syz_fuse_mount #define __NR_syz_fuse_mount 1000004 #endif #ifndef __NR_syz_fuseblk_mount #define __NR_syz_fuseblk_mount 1000005 #endif #ifndef __NR_syz_open_dev #define __NR_syz_open_dev 1000002 #endif #ifndef __NR_syz_open_pts #define __NR_syz_open_pts 1000003 #endif #ifndef __NR_syz_test #define __NR_syz_test 1000001 #endif #include <sys/ioctl.h> #include <sys/socket.h> #include <sys/stat.h> #include <sys/syscall.h> #include <sys/types.h> #include <net/if_arp.h> #include <errno.h> #include <error.h> #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 <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[17]; int main() { install_segv_handler(); memset(r, -1, sizeof(r)); r[0] = execute_syscall(__NR_mmap, 0x20000000ul, 0x35000ul, 0x3ul, 0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0); r[1] = execute_syscall(__NR_socket, 0xaul, 0x2ul, 0x88ul, 0, 0, 0, 0, 0, 0); NONFAILING(memcpy( (void*)0x20034000, "\x0a\x00\x42\x42\x7a\x85\x86\xb4\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x01\xb4\x73\x17\x84\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00", 128)); r[3] = execute_syscall(__NR_bind, r[1], 0x20034000ul, 0x80ul, 0, 0, 0, 0, 0, 0); NONFAILING(*(uint64_t*)0x2002b000 = (uint64_t)0x20021f80); NONFAILING(*(uint32_t*)0x2002b008 = (uint32_t)0x80); NONFAILING(*(uint64_t*)0x2002b010 = (uint64_t)0x2001f000); NONFAILING(*(uint64_t*)0x2002b018 = (uint64_t)0x0); NONFAILING(*(uint64_t*)0x2002b020 = (uint64_t)0x20027000); NONFAILING(*(uint64_t*)0x2002b028 = (uint64_t)0x0); NONFAILING(*(uint32_t*)0x2002b030 = (uint32_t)0x0); NONFAILING(memcpy( (void*)0x20021f80, "\x0a\x00\x42\x42\xbe\xf9\xa8\xa3\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x01\x7f\xdb\x0d\xf1\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" "\x00", 128)); r[12] = execute_syscall(__NR_sendmsg, r[1], 0x2002b000ul, 0x8000ul, 0, 0, 0, 0, 0, 0); NONFAILING(*(uint64_t*)0x20032fe0 = (uint64_t)0x20032000); NONFAILING(*(uint64_t*)0x20032fe8 = (uint64_t)0x1); NONFAILING(memcpy((void*)0x20032000, "\x0d", 1)); r[16] = execute_syscall(__NR_writev, r[1], 0x20032fe0ul, 0x1ul, 0, 0, 0, 0, 0, 0); return 0; }
