Date: Fri, 23 Feb 2024 23:44:06 +0800
From: xingwei lee <xrivendell7@...il.com>
To: syzbot+f0d29b273acdcd3a2562@...kaller.appspotmail.com
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org, 
	daniel@...earbox.net, haoluo@...gle.com, john.fastabend@...il.com, 
	jolsa@...nel.org, kpsingh@...nel.org, linux-kernel@...r.kernel.org, 
	martin.lau@...ux.dev, sdf@...gle.com, song@...nel.org, 
	syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] KMSAN: uninit-value in bstr_printf

Hello, I reproduced this bug in the upstream linux.

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

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

=====================================================
BUG: KMSAN: uninit-value in bstr_printf+0x1c57/0x1e30 lib/vsprintf.c:3334
 bstr_printf+0x1c57/0x1e30 lib/vsprintf.c:3334
 ____bpf_snprintf kernel/bpf/helpers.c:1064 [inline]
 bpf_snprintf+0x1eb/0x3c0 kernel/bpf/helpers.c:1044
 ___bpf_prog_run+0x232b/0xe6a0 kernel/bpf/core.c:1986
 __bpf_prog_run288+0xc0/0xf0 kernel/bpf/core.c:2226
 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline]
 bpf_flow_dissect+0x13c/0x490 net/core/flow_dissector.c:991
 bpf_prog_test_run_flow_dissector+0x78c/0xad0 net/bpf/test_run.c:1359
 bpf_prog_test_run+0x74c/0xb90 kernel/bpf/syscall.c:4107
 __sys_bpf+0x73b/0xfe0 kernel/bpf/syscall.c:5475
 __do_sys_bpf kernel/bpf/syscall.c:5561 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5559 [inline]
 __x64_sys_bpf+0xa9/0xf0 kernel/bpf/syscall.c:5559
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b


=* repro.c =*
// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define _GNU_SOURCE

#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.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>

#include <linux/futex.h>

#ifndef __NR_bpf
#define __NR_bpf 321
#endif

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;
}

static void thread_start(void* (*fn)(void*), void* arg) {
  pthread_t th;
  pthread_attr_t attr;
  pthread_attr_init(&attr);
  pthread_attr_setstacksize(&attr, 128 << 10);
  int i = 0;
  for (; i < 100; i++) {
    if (pthread_create(&th, &attr, fn, arg) == 0) {
      pthread_attr_destroy(&attr);
      return;
    }
    if (errno == EAGAIN) {
      usleep(50);
      continue;
    }
    break;
  }
  exit(1);
}

typedef struct {
  int state;
} event_t;

static void event_init(event_t* ev) {
  ev->state = 0;
}

static void event_reset(event_t* ev) {
  ev->state = 0;
}

static void event_set(event_t* ev) {
  if (ev->state)
    exit(1);
  __atomic_store_n(&ev->state, 1, __ATOMIC_RELEASE);
  syscall(SYS_futex, &ev->state, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1000000);
}

static void event_wait(event_t* ev) {
  while (!__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
    syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, 0);
}

static int event_isset(event_t* ev) {
  return __atomic_load_n(&ev->state, __ATOMIC_ACQUIRE);
}

static int event_timedwait(event_t* ev, uint64_t timeout) {
  uint64_t start = current_time_ms();
  uint64_t now = start;
  for (;;) {
    uint64_t remain = timeout - (now - start);
    struct timespec ts;
    ts.tv_sec = remain / 1000;
    ts.tv_nsec = (remain % 1000) * 1000 * 1000;
    syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, &ts);
    if (__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
      return 1;
    now = current_time_ms();
    if (now - start > timeout)
      return 0;
  }
}

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");
}

struct thread_t {
  int created, call;
  event_t ready, done;
};

static struct thread_t threads[16];
static void execute_call(int call);
static int running;

static void* thr(void* arg) {
  struct thread_t* th = (struct thread_t*)arg;
  for (;;) {
    event_wait(&th->ready);
    event_reset(&th->ready);
    execute_call(th->call);
    __atomic_fetch_sub(&running, 1, __ATOMIC_RELAXED);
    event_set(&th->done);
  }
  return 0;
}

static void execute_one(void) {
  int i, call, thread;
  for (call = 0; call < 6; call++) {
    for (thread = 0; thread < (int)(sizeof(threads) / sizeof(threads[0]));
         thread++) {
      struct thread_t* th = &threads[thread];
      if (!th->created) {
        th->created = 1;
        event_init(&th->ready);
        event_init(&th->done);
        event_set(&th->done);
        thread_start(thr, th);
      }
      if (!event_isset(&th->done))
        continue;
      event_reset(&th->done);
      th->call = call;
      __atomic_fetch_add(&running, 1, __ATOMIC_RELAXED);
      event_set(&th->ready);
      event_timedwait(&th->done, 50);
      break;
    }
  }
  for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++)
    sleep_ms(1);
}

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[4] = {0xffffffffffffffff, 0xffffffffffffffff, 0xffffffffffffffff,
                 0xffffffffffffffff};

void execute_call(int call) {
  intptr_t res = 0;
  switch (call) {
    case 0:
      *(uint32_t*)0x20000340 = 2;
      *(uint32_t*)0x20000344 = 4;
      *(uint32_t*)0x20000348 = 8;
      *(uint32_t*)0x2000034c = 1;
      *(uint32_t*)0x20000350 = 0x80;
      *(uint32_t*)0x20000354 = 0;
      *(uint32_t*)0x20000358 = 0;
      memset((void*)0x2000035c, 0, 16);
      *(uint32_t*)0x2000036c = 0;
      *(uint32_t*)0x20000370 = -1;
      *(uint32_t*)0x20000374 = 0;
      *(uint32_t*)0x20000378 = 0;
      *(uint32_t*)0x2000037c = 0;
      *(uint64_t*)0x20000380 = 0;
      res =
          syscall(__NR_bpf, /*cmd=*/0ul, /*arg=*/0x20000340ul, /*size=*/0x48ul);
      if (res != -1)
        r[0] = res;
      break;
    case 1:
      *(uint32_t*)0x20000180 = r[0];
      *(uint64_t*)0x20000188 = 0x20000100;
      *(uint32_t*)0x20000100 = 0;
      *(uint64_t*)0x20000190 = 0x20000140;
      memcpy((void*)0x20000140, "%pi6   \000", 8);
      *(uint64_t*)0x20000198 = 0;
      res =
          syscall(__NR_bpf, /*cmd=*/2ul, /*arg=*/0x20000180ul, /*size=*/0x20ul);
      if (res != -1)
        r[1] = *(uint32_t*)0x20000180;
      break;
    case 2:
      *(uint32_t*)0x20000440 = r[1];
      *(uint64_t*)0x20000448 = 0x200002c0;
      *(uint32_t*)0x200002c0 = 0;
      *(uint64_t*)0x20000450 = 0x20000400;
      memcpy((void*)0x20000400, "%pS    \000", 8);
      *(uint64_t*)0x20000458 = 0;
      syscall(__NR_bpf, /*cmd=*/2ul, /*arg=*/0x20000440ul, /*size=*/0x20ul);
      break;
    case 3:
      *(uint32_t*)0x200000c0 = r[1];
      res =
          syscall(__NR_bpf, /*cmd=*/0x16ul, /*arg=*/0x200000c0ul, /*size=*/4ul);
      if (res != -1)
        r[2] = *(uint32_t*)0x200000c0;
      break;
    case 4:
      *(uint32_t*)0x200004c0 = 0x16;
      *(uint32_t*)0x200004c4 = 0x10;
      *(uint64_t*)0x200004c8 = 0x20000040;
      memcpy((void*)0x20000040,
             "\x18\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
             "\xb7\x08\x00\x00\x00\x00\x00\x00\x7b\x8a\xf8\xff\x00\x00\x00\x00"
             "\xb7\x08\x00\x00\xff\xff\x0b\x86\x7b\x8a\xf0\xff\x00\x00\x00\x00"
             "\xbf\xa1\x00\x00\x00\x00\x00\x00\x07\x01\x00\x00\xf8\xff\xff\xff"
             "\xbf\xa4\x00\x00\x00\x00\x00\x00\x07\x04\x00\x00\xf0\xfe\xff\xff"
             "\xb7\x02\x00\x00\x08\x00\x00\x00\x18\x23\x00\x00",
             92);
      *(uint32_t*)0x2000009c = r[2];
      memcpy((void*)0x200000a0,
             "\x00\x00\x00\x00\x00\x00\x00\x00\xb7\x05\x00\x00\x08\x00\x00\x00"
             "\x85\x00\x00\x00\xa5\x00\x00\x00\x95",
             25);
      *(uint64_t*)0x200004d0 = 0x20000600;
      memcpy((void*)0x20000600, "GPL\000", 4);
      *(uint32_t*)0x200004d8 = 0;
      *(uint32_t*)0x200004dc = 0;
      *(uint64_t*)0x200004e0 = 0;
      *(uint32_t*)0x200004e8 = 0;
      *(uint32_t*)0x200004ec = 0;
      memset((void*)0x200004f0, 0, 16);
      *(uint32_t*)0x20000500 = 0;
      *(uint32_t*)0x20000504 = 0;
      *(uint32_t*)0x20000508 = 0;
      *(uint32_t*)0x2000050c = 0;
      *(uint64_t*)0x20000510 = 0;
      *(uint32_t*)0x20000518 = 0;
      *(uint32_t*)0x2000051c = 0;
      *(uint64_t*)0x20000520 = 0;
      *(uint32_t*)0x20000528 = 0;
      *(uint32_t*)0x2000052c = 0;
      *(uint32_t*)0x20000530 = 0;
      *(uint32_t*)0x20000534 = 0;
      *(uint64_t*)0x20000538 = 0;
      *(uint64_t*)0x20000540 = 0;
      *(uint32_t*)0x20000548 = 0;
      *(uint32_t*)0x2000054c = 0;
      res =
          syscall(__NR_bpf, /*cmd=*/5ul, /*arg=*/0x200004c0ul, /*size=*/0x90ul);
      if (res != -1)
        r[3] = res;
      break;
    case 5:
      *(uint32_t*)0x20000640 = r[3];
      *(uint32_t*)0x20000644 = 0;
      *(uint32_t*)0x20000648 = 0xe;
      *(uint32_t*)0x2000064c = 0;
      *(uint64_t*)0x20000650 = 0x20000000;
      memcpy((void*)0x20000000,
             "\x40\xf0\x53\x8e\xf0\x47\xb2\x1f\xb6\x00\x68\x30\x55\x00", 14);
      *(uint64_t*)0x20000658 = 0;
      *(uint32_t*)0x20000660 = 0;
      *(uint32_t*)0x20000664 = 0;
      *(uint32_t*)0x20000668 = 0;
      *(uint32_t*)0x2000066c = 0;
      *(uint64_t*)0x20000670 = 0;
      *(uint64_t*)0x20000678 = 0;
      *(uint32_t*)0x20000680 = 0;
      *(uint32_t*)0x20000684 = 0;
      *(uint32_t*)0x20000688 = 0;
      syscall(__NR_bpf, /*cmd=*/0xaul, /*arg=*/0x20000640ul, /*size=*/0x50ul);
      break;
  }
}
int main(void) {
  syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul,
          /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1,
          /*offset=*/0ul);
  syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul,
          /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/ 7ul,
          /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1,
          /*offset=*/0ul);
  syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul,
          /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1,
          /*offset=*/0ul);
  loop();
  return 0;
}


Remember to run this repro.txt with the command: syz-execprog -repeat
0 ./repro.txt.

=* repro.txt =*
r0 = bpf$MAP_CREATE_CONST_STR(0x0, &(0x7f0000000340)={0x2, 0x4, 0x8,
0x1, 0x80, 0x0}, 0x48)
bpf$MAP_UPDATE_CONST_STR(0x2, &(0x7f0000000180)={{r0,
<r1=>0xffffffffffffffff}, &(0x7f0000000100), &(0x7f0000000140)='%pi6
\x00'}, 0x20)
bpf$MAP_UPDATE_CONST_STR(0x2, &(0x7f0000000440)={{r1},
&(0x7f00000002c0), &(0x7f0000000400)='%pS    \x00'}, 0x20)
bpf$BPF_MAP_CONST_STR_FREEZE(0x16, &(0x7f00000000c0)={r1,
<r2=>0xffffffffffffffff}, 0x4)
r3 = bpf$PROG_LOAD(0x5, &(0x7f00000004c0)={0x16, 0x10,
&(0x7f0000000040)=ANY=[@ANYBLOB="18000000000000000000000000000000b7080000000000007b8af8ff00000000b7080000ffff0b867b8af0ff00000000bfa100000000000007010000f8ffffffbfa400000000000007040000f0feffffb70200000800000018230000",
@ANYRES32=r2, @ANYBLOB="0000000000000000b70500000800000085000000a500000095"],
&(0x7f0000000600)='GPL\x00', 0x0, 0x0, 0x0, 0x0, 0x0, '\x00', 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
0x90)
bpf$BPF_PROG_TEST_RUN(0xa, &(0x7f0000000640)={r3, 0x0, 0xe, 0x0,
&(0x7f0000000000)="40f0538ef047b21fb60068305500", 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0}, 0x50)

and see also in
https://gist.github.com/xrivendell7/baaee5029b1b1d05c66888c29fc1843f.
BTW, this bug maybe similar to this one:
https://syzkaller.appspot.com/bug?extid=c2dc95f7d0825a145992

I hope it helps.
Best regards!
xingwei Lee

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