Re: [syzbot] [netfilter?] KMSAN: uninit-value in __nla_validate_parse (3)

[xingwei lee]

Hello, I reproduced this bug in the syzbot dashboard and upstream linux.

If you fix this issue, please add the following tag to the commit:
Reported-by: xingwei lee <xrivendell7@xxxxxxxxx>

I use the same config with syzbot dashboard.
kernel version: c1ca10ceffbb289ed02feaf005bc9ee6095b4507
kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=e3dd779fba027968
with KMSAN enabled
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

[  254.423842][ T8047] =====================================================
[  254.430576][ T8047] BUG: KMSAN: uninit-value in
__nla_validate_parse+0x3d62/0x4f90
[  254.434357][ T8047]  __nla_validate_parse+0x3d62/0x4f90
[  254.437054][ T8047]  __nla_parse+0x6a/0x80
[  254.439556][ T8047]  nfnetlink_rcv_msg+0x74c/0xed0
[  254.444928][ T8047]  netlink_rcv_skb+0x58f/0x6d0
[  254.447359][ T8047]  nfnetlink_rcv+0x3e8/0x4d10
[  254.449893][ T8047]  netlink_unicast+0x107c/0x13e0
[  254.452371][ T8047]  netlink_sendmsg+0x132c/0x1540
[  254.454791][ T8047]  ____sys_sendmsg+0xa5b/0xe70
[  254.456975][ T8047]  ___sys_sendmsg+0x2a7/0x3f0
[  254.459423][ T8047]  __x64_sys_sendmsg+0x342/0x510
[  254.461514][ T8047]  do_syscall_64+0xcf/0x1e0
[  254.463345][ T8047]  entry_SYSCALL_64_after_hwframe+0x63/0x6b
[  254.465643][ T8047]
[  254.466539][ T8047] Uninit was created at:
[  254.468194][ T8047]  kmem_cache_alloc_node+0x5cb/0xbc0
[  254.470272][ T8047]  kmalloc_reserve+0x14d/0x500
[  254.471882][ T8047]  __alloc_skb+0x385/0x820
[  254.473385][ T8047]  netlink_sendmsg+0xbd6/0x1540
[  254.475011][ T8047]  ____sys_sendmsg+0xa5b/0xe70
[  254.476534][ T8047]  ___sys_sendmsg+0x2a7/0x3f0
[  254.478039][ T8047]  __x64_sys_sendmsg+0x342/0x510
[  254.479628][ T8047]  do_syscall_64+0xcf/0x1e0
[  254.480995][ T8047]  entry_SYSCALL_64_after_hwframe+0x63/0x6b
[  254.482719][ T8047]


=* repro.c =*
#define _GNU_SOURCE

#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

static void sleep_ms(uint64_t ms) {
  usleep(ms * 1000);
}

static uint64_t current_time_ms(void) {
  struct timespec ts;
  if (clock_gettime(CLOCK_MONOTONIC, &ts))
    exit(1);
  return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
}

#define BITMASK(bf_off, bf_len) (((1ull << (bf_len)) - 1) << (bf_off))
#define STORE_BY_BITMASK(type, htobe, addr, val, bf_off, bf_len)     \
  *(type*)(addr) =                                                   \
      htobe((htobe(*(type*)(addr)) & ~BITMASK((bf_off), (bf_len))) | \
            (((type)(val) << (bf_off)) & BITMASK((bf_off), (bf_len))))

static bool write_file(const char* file, const char* what, ...) {
  char buf[1024];
  va_list args;
  va_start(args, what);
  vsnprintf(buf, sizeof(buf), what, args);
  va_end(args);
  buf[sizeof(buf) - 1] = 0;
  int len = strlen(buf);
  int fd = open(file, O_WRONLY | O_CLOEXEC);
  if (fd == -1)
    return false;
  if (write(fd, buf, len) != len) {
    int err = errno;
    close(fd);
    errno = err;
    return false;
  }
  close(fd);
  return true;
}

static void kill_and_wait(int pid, int* status) {
  kill(-pid, SIGKILL);
  kill(pid, SIGKILL);
  for (int i = 0; i < 100; i++) {
    if (waitpid(-1, status, WNOHANG | __WALL) == pid)
      return;
    usleep(1000);
  }
  DIR* dir = opendir("/sys/fs/fuse/connections");
  if (dir) {
    for (;;) {
      struct dirent* ent = readdir(dir);
      if (!ent)
        break;
      if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
        continue;
      char abort[300];
      snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",
               ent->d_name);
      int fd = open(abort, O_WRONLY);
      if (fd == -1) {
        continue;
      }
      if (write(fd, abort, 1) < 0) {
      }
      close(fd);
    }
    closedir(dir);
  } else {
  }
  while (waitpid(-1, status, __WALL) != pid) {
  }
}

static void setup_test() {
  prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
  setpgrp();
  write_file("/proc/self/oom_score_adj", "1000");
}

static void execute_one(void);

#define WAIT_FLAGS __WALL

static void loop(void) {
  int iter = 0;
  for (;; iter++) {
    int pid = fork();
    if (pid < 0)
      exit(1);
    if (pid == 0) {
      setup_test();
      execute_one();
      exit(0);
    }
    int status = 0;
    uint64_t start = current_time_ms();
    for (;;) {
      if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
        break;
      sleep_ms(1);
      if (current_time_ms() - start < 5000)
        continue;
      kill_and_wait(pid, &status);
      break;
    }
  }
}

uint64_t r[1] = {0xffffffffffffffff};

void execute_one(void) {
  intptr_t res = 0;
  res = syscall(__NR_socket, /*domain=*/0x10ul, /*type=*/3ul, /*proto=*/0xc);
  if (res != -1)
    r[0] = res;
  *(uint64_t*)0x20000080 = 0;
  *(uint32_t*)0x20000088 = 0;
  *(uint64_t*)0x20000090 = 0x20000040;
  *(uint64_t*)0x20000040 = 0x20000100;
  *(uint32_t*)0x20000100 = 0x18;
  *(uint8_t*)0x20000104 = 0;
  *(uint8_t*)0x20000105 = 0xb;
  *(uint16_t*)0x20000106 = 0x401;
  *(uint32_t*)0x20000108 = 0;
  *(uint32_t*)0x2000010c = 0;
  *(uint8_t*)0x20000110 = 0;
  *(uint8_t*)0x20000111 = 0;
  *(uint16_t*)0x20000112 = htobe16(0);
  *(uint16_t*)0x20000114 = 4;
  STORE_BY_BITMASK(uint16_t, , 0x20000116, 2, 0, 14);
  STORE_BY_BITMASK(uint16_t, , 0x20000117, 0, 6, 1);
  STORE_BY_BITMASK(uint16_t, , 0x20000117, 1, 7, 1);
  *(uint64_t*)0x20000048 = 0x18;
  *(uint64_t*)0x20000098 = 1;
  *(uint64_t*)0x200000a0 = 0;
  *(uint64_t*)0x200000a8 = 0;
  *(uint32_t*)0x200000b0 = 0;
  syscall(__NR_sendmsg, /*fd=*/r[0], /*msg=*/0x20000080ul, /*f=*/0ul);
}
int main(void) {
  syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul, /*prot=*/7ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  loop();
  return 0;
}

=* repro.txt =*
r0 = socket$nl_netfilter(0x10, 0x3, 0xc)
sendmsg$IPCTNL_MSG_CT_NEW(r0, &(0x7f0000000080)={0x0, 0x0,
&(0x7f0000000040)={&(0x7f0000000100)={0x18, 0x0, 0xb, 0x401, 0x0, 0x0,
{}, [@CTA_TUPLE_REPLY={0x4}]}, 0x18}}, 0x0)


and see also in
https://gist.github.com/xrivendell7/fe97316e8a66f8d81109a158a3225bc0

I hope it helps.
Best regards!
xingwei Lee