net/sctp: null-ptr-deref in sctp_put_port/sctp_endpoint_destroy

From: Andrey Konovalov
Date: Wed Feb 08 2017 - 14:05:58 EST

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Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On commit 926af6273fc683cd98cd0ce7bf0d04a02eed6742.

A reproducer and .config are attached.

general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 3 PID: 19506 Comm: syz-executor0 Not tainted 4.10.0-rc7+ #126
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88003d7c1700 task.stack: ffff880037990000
RIP: 0010:__write_once_size include/linux/compiler.h:272 [inline]
RIP: 0010:__hlist_del include/linux/list.h:635 [inline]
RIP: 0010:__sk_del_bind_node include/net/sock.h:685 [inline]
RIP: 0010:__sctp_put_port net/sctp/socket.c:6994 [inline]
RIP: 0010:sctp_put_port+0x210/0x620 net/sctp/socket.c:7004
RSP: 0018:ffff8800379969e0 EFLAGS: 00010246
RAX: dffffc0000000010 RBX: 1ffff10006f32d41 RCX: ffff880037996a28
RDX: 0000000000000000 RSI: 0000000000000000 RDI: dffffc0000000000
RBP: ffff880037996b10 R08: 0000000000000000 R09: 0000000000000000
R10: 1c8b9dfca637effe R11: dffffc0000000000 R12: 0000000000000005
R13: ffff880037996ae8 R14: ffff88003a066c40 R15: ffff88003a067178
FS: 00007fd314dba700(0000) GS:ffff88006df00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020002ffc CR3: 000000003b10e000 CR4: 00000000000006e0
Call Trace:
sctp_endpoint_destroy net/sctp/endpointola.c:275 [inline]
sctp_endpoint_put+0x1b2/0x260 net/sctp/endpointola.c:296
sctp_endpoint_free+0x97/0xc0 net/sctp/endpointola.c:238
sctp_destroy_sock+0xd6/0x470 net/sctp/socket.c:4254
sctp_v6_destroy_sock+0x15/0x20 net/sctp/socket.c:7871
sk_common_release+0xbf/0x4e0 net/core/sock.c:2747
sctp_close+0x764/0x9f0 net/sctp/socket.c:1550
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 [inline]
do_exit+0x186b/0x2800 kernel/exit.c:839
do_group_exit+0x149/0x420 kernel/exit.c:943
get_signal+0x76d/0x17e0 kernel/signal.c:2313
do_signal+0xd2/0x2190 arch/x86/kernel/signal.c:807
exit_to_usermode_loop+0x170/0x200 arch/x86/entry/common.c:156
prepare_exit_to_usermode arch/x86/entry/common.c:190 [inline]
syscall_return_slowpath+0x3d3/0x420 arch/x86/entry/common.c:259
entry_SYSCALL_64_fastpath+0xc0/0xc2
RIP: 0033:0x4458b9
RSP: 002b:00007fd314db9cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 0000000000708170 RCX: 00000000004458b9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000708170
RBP: 0000000000708150 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fd314dba9c0 R15: 00007fd314dba700
Code: ff ff ff 49 8b 76 20 48 bf 00 00 00 00 00 fc ff df 49 89 c8 49
c1 e8 03 41 c6 04 38 00 49 89 f0 49 89 95 40 ff ff ff 49 c1 e8 03 <41>
80 3c 38 00 0f 85 f6 02 00 00 48 c1 e9 03 49 b8 00 00 00 00
RIP: __write_once_size include/linux/compiler.h:272 [inline] RSP:
ffff8800379969e0
RIP: __hlist_del include/linux/list.h:635 [inline] RSP: ffff8800379969e0
RIP: __sk_del_bind_node include/net/sock.h:685 [inline] RSP: ffff8800379969e0
RIP: __sctp_put_port net/sctp/socket.c:6994 [inline] RSP: ffff8800379969e0
RIP: sctp_put_port+0x210/0x620 net/sctp/socket.c:7004 RSP: ffff8800379969e0
---[ end trace 54c316f8731a5a88 ]---
Kernel panic - not syncing: Fatal exception in interrupt
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

Attachment: .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_setsockopt
#define __NR_setsockopt 54
#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[4];
void loop()
{
memset(r, -1, sizeof(r));
r[0] = execute_syscall(__NR_mmap, 0x20000000ul, 0xef0000ul, 0x3ul,
0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0);
r[1] = execute_syscall(__NR_socket, 0xaul, 0x5ul, 0x84ul, 0, 0, 0, 0,
0, 0);
NONFAILING(*(uint32_t*)0x2051d000 = (uint32_t)0x5);
r[3] = execute_syscall(__NR_setsockopt, r[1], 0x29ul, 0xd1ul,
0x2051d000ul, 0x4ul, 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;
}

Next message: Ingo Molnar: "[PATCH 29/35] sched/core: Remove unused prefetch_stack()"
Previous message: Ingo Molnar: "[PATCH 18/35] sched/headers: Remove <linux/rtmutex.h> from <linux/sched.h>"
Next in thread: Xin Long: "Re: net/sctp: null-ptr-deref in sctp_put_port/sctp_endpoint_destroy"
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