Re: [syzbot] [nilfs?] KMSAN: uninit-value in nilfs_add_checksums_on_logs (2)

[xingwei lee <xrivendell7@gmail.com>]

Hello, I reproduced this bug.

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

Notice: I use the same config with syzbot dashboard.
kernel version: e326df53af0021f48a481ce9d489efda636c2dc6
kernel config: https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
with KMSAN enabled
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

=====================================================
BUG: KMSAN: uninit-value in crc32_body lib/crc32.c:110 [inline]
BUG: KMSAN: uninit-value in crc32_le_generic lib/crc32.c:179 [inline]
BUG: KMSAN: uninit-value in crc32_le_base+0x475/0xe70 lib/crc32.c:197
crc32_body lib/crc32.c:110 [inline]
crc32_le_generic lib/crc32.c:179 [inline]
crc32_le_base+0x475/0xe70 lib/crc32.c:197
nilfs_segbuf_fill_in_data_crc fs/nilfs2/segbuf.c:224 [inline]
nilfs_add_checksums_on_logs+0xcb2/0x10a0 fs/nilfs2/segbuf.c:327
nilfs_segctor_do_construct+0xad1d/0xf640 fs/nilfs2/segment.c:2112
nilfs_segctor_construct+0x1fd/0xf30 fs/nilfs2/segment.c:2415
nilfs_segctor_thread_construct fs/nilfs2/segment.c:2523 [inline]
nilfs_segctor_thread+0x551/0x1350 fs/nilfs2/segment.c:2606
kthread+0x422/0x5a0 kernel/kthread.c:388
ret_from_fork+0x7f/0xa0 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
Uninit was created at:
__alloc_pages+0x9a8/0xe00 mm/page_alloc.c:4591
alloc_pages_mpol+0x6b3/0xaa0 mm/mempolicy.c:2133
alloc_pages mm/mempolicy.c:2204 [inline]
folio_alloc+0x218/0x3f0 mm/mempolicy.c:2211
filemap_alloc_folio+0xb8/0x4b0 mm/filemap.c:974
__filemap_get_folio+0xa8a/0x1910 mm/filemap.c:1918
pagecache_get_page+0x56/0x1d0 mm/folio-compat.c:99
grab_cache_page_write_begin+0x61/0x80 mm/folio-compat.c:109
block_write_begin+0x5a/0x4a0 fs/buffer.c:2223
nilfs_write_begin+0x107/0x220 fs/nilfs2/inode.c:261
generic_perform_write+0x417/0xce0 mm/filemap.c:3927
__generic_file_write_iter+0x233/0x4b0 mm/filemap.c:4022
generic_file_write_iter+0x10e/0x600 mm/filemap.c:4048
__kernel_write_iter+0x365/0xa00 fs/read_write.c:523
dump_emit_page fs/coredump.c:888 [inline]
dump_user_range+0x5d7/0xe00 fs/coredump.c:915
elf_core_dump+0x5847/0x5fa0 fs/binfmt_elf.c:2077
do_coredump+0x3bb6/0x4e60 fs/coredump.c:764
get_signal+0x28f7/0x30b0 kernel/signal.c:2890
arch_do_signal_or_restart+0x5e/0xda0 arch/x86/kernel/signal.c:309
exit_to_user_mode_loop kernel/entry/common.c:105 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
irqentry_exit_to_user_mode+0xaa/0x160 kernel/entry/common.c:225
irqentry_exit+0x16/0x40 kernel/entry/common.c:328
exc_page_fault+0x246/0x6f0 arch/x86/mm/fault.c:1566
asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:570
CPU: 1 PID: 11178 Comm: segctord Not tainted 6.7.0-00562-g9f8413c4a66f-dirty #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.16.2-debian-1.16.2-1 04/01/2014
=====================================================

=* repro.c =*
#define _GNU_SOURCE

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

#include <linux/capability.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;
}

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;
}

#define MAX_FDS 30

static void setup_common()
{
 if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {
 }
}

static void setup_binderfs()
{
 if (mkdir("/dev/binderfs", 0777)) {
 }
 if (mount("binder", "/dev/binderfs", "binder", 0, NULL)) {
 }
 if (symlink("/dev/binderfs", "./binderfs")) {
 }
}

static void loop();

static void sandbox_common()
{
 prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
 setsid();
 struct rlimit rlim;
 rlim.rlim_cur = rlim.rlim_max = (200 << 20);
 setrlimit(RLIMIT_AS, &rlim);
 rlim.rlim_cur = rlim.rlim_max = 32 << 20;
 setrlimit(RLIMIT_MEMLOCK, &rlim);
 rlim.rlim_cur = rlim.rlim_max = 136 << 20;
 setrlimit(RLIMIT_FSIZE, &rlim);
 rlim.rlim_cur = rlim.rlim_max = 1 << 20;
 setrlimit(RLIMIT_STACK, &rlim);
 rlim.rlim_cur = rlim.rlim_max = 128 << 20;
 setrlimit(RLIMIT_CORE, &rlim);
 rlim.rlim_cur = rlim.rlim_max = 256;
 setrlimit(RLIMIT_NOFILE, &rlim);
 if (unshare(CLONE_NEWNS)) {
 }
 if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
 }
 if (unshare(CLONE_NEWIPC)) {
 }
 if (unshare(0x02000000)) {
 }
 if (unshare(CLONE_NEWUTS)) {
 }
 if (unshare(CLONE_SYSVSEM)) {
 }
 typedef struct {
   const char* name;
   const char* value;
 } sysctl_t;
 static const sysctl_t sysctls[] = {
     {"/proc/sys/kernel/shmmax", "16777216"},
     {"/proc/sys/kernel/shmall", "536870912"},
     {"/proc/sys/kernel/shmmni", "1024"},
     {"/proc/sys/kernel/msgmax", "8192"},
     {"/proc/sys/kernel/msgmni", "1024"},
     {"/proc/sys/kernel/msgmnb", "1024"},
     {"/proc/sys/kernel/sem", "1024 1048576 500 1024"},
 };
 unsigned i;
 for (i = 0; i < sizeof(sysctls) / sizeof(sysctls[0]); i++)
   write_file(sysctls[i].name, sysctls[i].value);
}

static int wait_for_loop(int pid)
{
 if (pid < 0)
   exit(1);
 int status = 0;
 while (waitpid(-1, &status, __WALL) != pid) {
 }
 return WEXITSTATUS(status);
}

static void drop_caps(void)
{
 struct __user_cap_header_struct cap_hdr = {};
 struct __user_cap_data_struct cap_data[2] = {};
 cap_hdr.version = _LINUX_CAPABILITY_VERSION_3;
 cap_hdr.pid = getpid();
 if (syscall(SYS_capget, &cap_hdr, &cap_data))
   exit(1);
 const int drop = (1 << CAP_SYS_PTRACE) | (1 << CAP_SYS_NICE);
 cap_data[0].effective &= ~drop;
 cap_data[0].permitted &= ~drop;
 cap_data[0].inheritable &= ~drop;
 if (syscall(SYS_capset, &cap_hdr, &cap_data))
   exit(1);
}

static int do_sandbox_none(void)
{
 if (unshare(CLONE_NEWPID)) {
 }
 int pid = fork();
 if (pid != 0)
   return wait_for_loop(pid);
 setup_common();
 sandbox_common();
 drop_caps();
 if (unshare(CLONE_NEWNET)) {
 }
 write_file("/proc/sys/net/ipv4/ping_group_range", "0 65535");
 setup_binderfs();
 loop();
 exit(1);
}

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 close_fds()
{
 for (int fd = 3; fd < MAX_FDS; fd++)
   close(fd);
}

#define USLEEP_FORKED_CHILD (3 * 50 * 1000)

static long handle_clone_ret(long ret)
{
 if (ret != 0) {
   return ret;
 }
 usleep(USLEEP_FORKED_CHILD);
 syscall(__NR_exit, 0);
 while (1) {
 }
}

static long syz_clone(volatile long flags, volatile long stack,
                     volatile long stack_len, volatile long ptid,
                     volatile long ctid, volatile long tls)
{
 long sp = (stack + stack_len) & ~15;
 long ret = (long)syscall(__NR_clone, flags & ~CLONE_VM, sp, ptid, ctid, tls);
 return handle_clone_ret(ret);
}

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();
     close_fds();
     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;
   }
 }
}

void execute_one(void)
{
 syz_clone(/*flags=CLONE_IO*/ 0x80000000, /*stack=*/0x20000140,
           /*stack_len=*/0, /*parentid=*/0, /*childtid=*/0, /*tls=*/0);
}
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);
 do_sandbox_none();
 return 0;
}


Remember to run this repro.txt with the command: syz-execprog -repeat
0 ./repro.txt and wait for about 1minus, the bug triggered very
steady.

=* repro.txt =*
syz_mount_image$nilfs2(&(0x7f0000000000),
&(0x7f0000000a80)='./file0\x00', 0x808, &(0x7f00000000c0)=ANY=[], 0x1,
0xa4a, &(0x7f0000001540)="$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")
r0 = open(&(0x7f0000000000)='./bus\x00', 0x0, 0x0) (async)
r1 = open(&(0x7f0000007f80)='./bus\x00', 0x145142, 0x0)
cachestat(r1, &(0x7f00000002c0)={0x6}, &(0x7f0000000300), 0x0) (async)
r2 = syz_open_procfs(0xffffffffffffffff,
&(0x7f0000000100)='mountinfo\x00') (async)
r3 = open(&(0x7f0000000a40)='./bus\x00', 0x141a42, 0x0)
r4 = openat$adsp1(0xffffffffffffff9c, &(0x7f0000000040), 0x20000, 0x0) (async)
ptrace(0x10, 0x0) (async)
r5 = syz_clone(0x80000000,
&(0x7f0000000140)="1d7f3ef3f0b0129f8d083226510ecc0713b2af6e7901a607532fa2a7176fefdd7e66e6402ef8b579a00dd83d555182afa044f65b0ac668c2063ac33b34bb48411c11d456d584ec4140aebe97e1950ad7c4bd2bffcef175625a27a11f559e8ddb031d27c2be3a2216a1e9f87f5d68b8b0b690e67bfcc8a8ec9af998c1a8eaef215c771e45eee015e8ce9b17015da79c48a7b87459c4a88781ffd9d1ec6870c4d7220ffc6a66f7828db1297aa12e00503dde7a5c",
0xb3, &(0x7f0000000080), &(0x7f00000000c0),
&(0x7f0000000200)="994665d2b9d5239b789d65f6ec184c1ea67003ce8f474755e439f58560c42a241a31e540479e0752cad17884d9024cb854dc6798ada62550c8264b5488daff5387419b22f01fa57630317e8c24ac37d892d70e380b7164dfaa886b72a17f08df76c1057a2268b39aad4e0e759eef1abc6e5e664e7f3057c1d70d897ba5104664e96d92c1d8bd420f78368f522169f713ed03315d69de28d77af27ec8881f54633a5dd5d54635e74ad8c896918c")
fcntl$setown(r4, 0x8, r5) (async)
sendfile(r3, r2, 0x0, 0x100800001) (async)
sendfile(r0, r1, 0x0, 0x1000000201003)


and see also in
https://gist.github.com/xrivendell7/744812c87156085e12c7f617ef237875.
BTW, found in my personal observation, the syzlang reproducer can
trigger the bug more stably, so try to use the syz-execprog -repeat 0
./repro.txt to trigger this bug.

I hope it helps.
Best regards!
xingwei Lee