Hi!
I've got the following error report while running the syzkaller fuzzer.
On commit a121103c922847ba5010819a3f250f1f7fc84ab8 (4.10-rc3).
A reproducer is attached.
==================================================================
BUG: KASAN: use-after-free in sock_wfree+0x118/0x120
Read of size 8 at addr ffff880062da0060 by task a.out/4140
page:ffffea00018b6800 count:1 mapcount:0 mapping: (null)
index:0x0 compound_mapcount: 0
flags: 0x100000000008100(slab|head)
raw: 0100000000008100 0000000000000000 0000000000000000 0000000180130013
raw: dead000000000100 dead000000000200 ffff88006741f140 0000000000000000
page dumped because: kasan: bad access detected
CPU: 0 PID: 4140 Comm: a.out Not tainted 4.10.0-rc3+ #59
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:15
dump_stack+0x292/0x398 lib/dump_stack.c:51
describe_address mm/kasan/report.c:262
kasan_report_error+0x121/0x560 mm/kasan/report.c:370
kasan_report mm/kasan/report.c:392
__asan_report_load8_noabort+0x3e/0x40 mm/kasan/report.c:413
sock_flag ./arch/x86/include/asm/bitops.h:324
sock_wfree+0x118/0x120 net/core/sock.c:1631
skb_release_head_state+0xfc/0x250 net/core/skbuff.c:655
skb_release_all+0x15/0x60 net/core/skbuff.c:668
__kfree_skb+0x15/0x20 net/core/skbuff.c:684
kfree_skb+0x16e/0x4e0 net/core/skbuff.c:705
inet_frag_destroy+0x121/0x290 net/ipv4/inet_fragment.c:304
inet_frag_put ./include/net/inet_frag.h:133
nf_ct_frag6_gather+0x1125/0x38b0 net/ipv6/netfilter/nf_conntrack_reasm.c:617
ipv6_defrag+0x21b/0x350 net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:68
nf_hook_entry_hookfn ./include/linux/netfilter.h:102
nf_hook_slow+0xc3/0x290 net/netfilter/core.c:310
nf_hook ./include/linux/netfilter.h:212
__ip6_local_out+0x52c/0xaf0 net/ipv6/output_core.c:160
ip6_local_out+0x2d/0x170 net/ipv6/output_core.c:170
ip6_send_skb+0xa1/0x340 net/ipv6/ip6_output.c:1722
ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1742
rawv6_push_pending_frames net/ipv6/raw.c:613
rawv6_sendmsg+0x2cff/0x4130 net/ipv6/raw.c:927
inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:744
sock_sendmsg_nosec net/socket.c:635
sock_sendmsg+0xca/0x110 net/socket.c:645
sock_write_iter+0x326/0x620 net/socket.c:848
new_sync_write fs/read_write.c:499
__vfs_write+0x483/0x760 fs/read_write.c:512
vfs_write+0x187/0x530 fs/read_write.c:560
SYSC_write fs/read_write.c:607
SyS_write+0xfb/0x230 fs/read_write.c:599
entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:203
RIP: 0033:0x7ff26e6f5b79
RSP: 002b:00007ff268e0ed98 EFLAGS: 00000206 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ff268e0f9c0 RCX: 00007ff26e6f5b79
RDX: 0000000000000010 RSI: 0000000020f50fe1 RDI: 0000000000000003
RBP: 00007ff26ebc1220 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007ff268e0f9c0 R14: 00007ff26efec040 R15: 0000000000000003
The buggy address belongs to the object at ffff880062da0000
which belongs to the cache RAWv6 of size 1504
The buggy address ffff880062da0060 is located 96 bytes inside
of 1504-byte region [ffff880062da0000, ffff880062da05e0)
Freed by task 4113:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
save_stack+0x43/0xd0 mm/kasan/kasan.c:502
set_track mm/kasan/kasan.c:514
kasan_slab_free+0x73/0xc0 mm/kasan/kasan.c:578
slab_free_hook mm/slub.c:1352
slab_free_freelist_hook mm/slub.c:1374
slab_free mm/slub.c:2951
kmem_cache_free+0xb2/0x2c0 mm/slub.c:2973
sk_prot_free net/core/sock.c:1377
__sk_destruct+0x49c/0x6e0 net/core/sock.c:1452
sk_destruct+0x47/0x80 net/core/sock.c:1460
__sk_free+0x57/0x230 net/core/sock.c:1468
sk_free+0x23/0x30 net/core/sock.c:1479
sock_put ./include/net/sock.h:1638
sk_common_release+0x31e/0x4e0 net/core/sock.c:2782
rawv6_close+0x54/0x80 net/ipv6/raw.c:1214
inet_release+0xed/0x1c0 net/ipv4/af_inet.c:425
inet6_release+0x50/0x70 net/ipv6/af_inet6.c:431
sock_release+0x8d/0x1e0 net/socket.c:599
sock_close+0x16/0x20 net/socket.c:1063
__fput+0x332/0x7f0 fs/file_table.c:208
____fput+0x15/0x20 fs/file_table.c:244
task_work_run+0x19b/0x270 kernel/task_work.c:116
exit_task_work ./include/linux/task_work.h:21
do_exit+0x186b/0x2800 kernel/exit.c:839
do_group_exit+0x149/0x420 kernel/exit.c:943
SYSC_exit_group kernel/exit.c:954
SyS_exit_group+0x1d/0x20 kernel/exit.c:952
entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:203
Allocated by task 4115:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
save_stack+0x43/0xd0 mm/kasan/kasan.c:502
set_track mm/kasan/kasan.c:514
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:605
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:544
slab_post_alloc_hook mm/slab.h:432
slab_alloc_node mm/slub.c:2708
slab_alloc mm/slub.c:2716
kmem_cache_alloc+0x1af/0x250 mm/slub.c:2721
sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1334
sk_alloc+0x105/0x1010 net/core/sock.c:1396
inet6_create+0x44d/0x1150 net/ipv6/af_inet6.c:183
__sock_create+0x4f6/0x880 net/socket.c:1199
sock_create net/socket.c:1239
SYSC_socket net/socket.c:1269
SyS_socket+0xf9/0x230 net/socket.c:1249
entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:203
Memory state around the buggy address:
ffff880062d9ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff880062d9ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff880062da0000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff880062da0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff880062da0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
// autogenerated by syzkaller (http://github.com/google/syzkaller)
#ifndef __NR_ioctl
#define __NR_ioctl 16
#endif
#ifndef __NR_mmap
#define __NR_mmap 9
#endif
#ifndef __NR_socket
#define __NR_socket 41
#endif
#ifndef __NR_connect
#define __NR_connect 42
#endif
#ifndef __NR_bind
#define __NR_bind 49
#endif
#ifndef __NR_sendto
#define __NR_sendto 44
#endif
#ifndef __NR_recvfrom
#define __NR_recvfrom 45
#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 <linux/capability.h>
#include <linux/if.h>
#include <linux/if_tun.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)
{
syscall(__NR_exit_group, status);
volatile unsigned i = 0;
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)
{
if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED))
_longjmp(segv_env, 1);
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); \
}
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(uint64_t pid, bool enable_tun)
{
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 pid = fork();
if (pid)
return pid;
sandbox_common();
loop();
doexit(1);
}
long r[56];
void* thr(void* arg)
{
switch ((long)arg) {
case 0:
r[0] =
execute_syscall(__NR_mmap, 0x20000000ul, 0xf55000ul, 0x3ul,
0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0);
break;
case 1:
r[1] = execute_syscall(__NR_socket, 0xaul, 0x3ul, 0x2cul, 0, 0, 0,
0, 0, 0);
break;
case 2:
NONFAILING(*(uint16_t*)0x20016000 = (uint16_t)0xa);
NONFAILING(*(uint16_t*)0x20016002 = (uint16_t)0x204e);
NONFAILING(*(uint32_t*)0x20016004 = (uint32_t)0x0);
NONFAILING(*(uint64_t*)0x20016008 = (uint64_t)0x0);
NONFAILING(*(uint64_t*)0x20016010 = (uint64_t)0x0);
NONFAILING(*(uint32_t*)0x20016018 = (uint32_t)0x0);
r[8] = execute_syscall(__NR_connect, r[1], 0x20016000ul, 0x20ul, 0,
0, 0, 0, 0, 0);
break;
case 3:
NONFAILING(*(uint16_t*)0x20373000 = (uint16_t)0x2);
NONFAILING(*(uint16_t*)0x20373002 = (uint16_t)0x204e);
NONFAILING(*(uint8_t*)0x20373004 = (uint8_t)0xc0);
NONFAILING(*(uint8_t*)0x20373005 = (uint8_t)0xa8);
NONFAILING(*(uint8_t*)0x20373006 = (uint8_t)0xda);
NONFAILING(*(uint8_t*)0x20373007 = (uint8_t)0xaa);
NONFAILING(*(uint8_t*)0x20373008 = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20373009 = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x2037300a = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x2037300b = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x2037300c = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x2037300d = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x2037300e = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x2037300f = (uint8_t)0x0);
r[23] = execute_syscall(__NR_bind, 0xfffffffffffffffful,
0x20373000ul, 0x10ul, 0, 0, 0, 0, 0, 0);
break;
case 4:
NONFAILING(*(uint16_t*)0x20f4a000 = (uint16_t)0x0);
NONFAILING(*(uint16_t*)0x20f4a002 = (uint16_t)0x204e);
NONFAILING(*(uint32_t*)0x20f4a004 = (uint32_t)0x0);
NONFAILING(*(uint8_t*)0x20f4a008 = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20f4a009 = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20f4a00a = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20f4a00b = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20f4a00c = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20f4a00d = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20f4a00e = (uint8_t)0x0);
NONFAILING(*(uint8_t*)0x20f4a00f = (uint8_t)0x0);
r[35] = execute_syscall(__NR_connect, 0xfffffffffffffffful,
0x20f4a000ul, 0x10ul, 0, 0, 0, 0, 0, 0);
break;
case 5:
NONFAILING(*(uint16_t*)0x20f4cfe0 = (uint16_t)0xa);
NONFAILING(*(uint16_t*)0x20f4cfe2 = (uint16_t)0x204e);
NONFAILING(*(uint32_t*)0x20f4cfe4 = (uint32_t)0x0);
NONFAILING(*(uint64_t*)0x20f4cfe8 = (uint64_t)0x0);
NONFAILING(*(uint64_t*)0x20f4cff0 = (uint64_t)0x100000000000000);
NONFAILING(*(uint32_t*)0x20f4cff8 = (uint32_t)0x5);
r[42] =
execute_syscall(__NR_sendto, 0xfffffffffffffffful, 0x20006000ul,
0x0ul, 0x0ul, 0x20f4cfe0ul, 0x20ul, 0, 0, 0);
break;
case 6:
r[43] = execute_syscall(__NR_recvfrom, 0xfffffffffffffffful,
0x20144f28ul, 0x0ul, 0x10000ul,
0x20f4e000ul, 0x0ul, 0, 0, 0);
break;
case 7:
r[44] = execute_syscall(__NR_socket, 0x1ful, 0x5ul, 0x2ul, 0, 0, 0,
0, 0, 0);
break;
case 8:
r[45] = execute_syscall(__NR_write, r[1], 0x20aa4fdaul, 0xfffful, 0,
0, 0, 0, 0, 0);
break;
case 9:
NONFAILING(*(uint32_t*)0x20f54000 = (uint32_t)0x0);
NONFAILING(*(uint32_t*)0x20f54004 = (uint32_t)0x0);
NONFAILING(*(uint64_t*)0x20f54008 = (uint64_t)0x0);
r[49] =
execute_syscall(__NR_ioctl, 0xfffffffffffffffful, 0xc010640bul,
0x20f54000ul, 0, 0, 0, 0, 0, 0);
break;
case 10:
NONFAILING(*(uint32_t*)0x20f54000 = (uint32_t)0x0);
NONFAILING(*(uint32_t*)0x20f54004 = (uint32_t)0x0);
NONFAILING(*(uint64_t*)0x20f54008 = (uint64_t)0xfc51);
r[53] =
execute_syscall(__NR_ioctl, 0xfffffffffffffffful, 0xc010640bul,
0x20f54000ul, 0, 0, 0, 0, 0, 0);
break;
case 11:
NONFAILING(memcpy((void*)0x20f50fe1, "\x1f\x00\x00\x80\x01\x00\x00"
"\x16\x00\x00\x00\x9a\xc7\x00"
"\x00\x06",
16));
r[55] = execute_syscall(__NR_write, r[1], 0x20f50fe1ul, 0x10ul, 0,
0, 0, 0, 0, 0);
break;
}
return 0;
}
void loop()
{
long i;
pthread_t th[24];
memset(r, -1, sizeof(r));
srand(getpid());
for (i = 0; i < 12; i++) {
pthread_create(&th[i], 0, thr, (void*)i);
usleep(10000);
}
for (i = 0; i < 12; i++) {
pthread_create(&th[12 + i], 0, thr, (void*)i);
if (rand() % 2)
usleep(rand() % 10000);
}
usleep(100000);
}
int main()
{
setup_main_process(0, false);
int pid = do_sandbox_none();
int status = 0;
while (waitpid(pid, &status, __WALL) != pid) {
}
return 0;
}
