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SubjectBUG: MAX_LOCKDEP_KEYS too low!
Date
Hi!

Syzkaller found this bug and it has a repro (below). I googled a similar
bug in 2019 which was fixed so this seems new.

The repro takes about a half a minute to produce the message, "grep
lock-classes /proc/lockdep_stats" reports 8177 of 8192, before running
the repro it is 702. It is a POWER8 box.

The offender is htab->lockdep_key. If I run repro at the slow rate, no
problems appears, traces show lockdep_unregister_key() is called and the
leak is quite slow.

Is this something known? Any hints how to debug this further? I'd give
it a try since I have an easy reproducer. Thanks,



root@le-dbg:~# egrep "BD.*htab->lockdep_key" /proc/lockdep | wc -l
7449
root@le-dbg:~# egrep "BD.*htab->lockdep_key" /proc/lockdep | tail -n 3
(____ptrval____) FD: 1 BD: 1 ....: &htab->lockdep_key#9531
(____ptrval____) FD: 1 BD: 1 ....: &htab->lockdep_key#9532
(____ptrval____) FD: 1 BD: 1 ....: &htab->lockdep_key#9533


// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define __unix__ 1
#define __gnu_linux__ 1
#define __linux__ 1

#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 unsigned long long procid;

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;
}

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;
}
}
}

#ifndef __NR_bpf
#define __NR_bpf 361
#endif
#ifndef __NR_mmap
#define __NR_mmap 90
#endif

uint64_t r[1] = {0xffffffffffffffff};

void execute_one(void)
{
intptr_t res = 0;
*(uint32_t*)0x20000280 = 9;
*(uint32_t*)0x20000284 = 1;
*(uint32_t*)0x20000288 = 6;
*(uint32_t*)0x2000028c = 5;
*(uint32_t*)0x20000290 = 0;
*(uint32_t*)0x20000294 = -1;
*(uint32_t*)0x20000298 = 0;
*(uint8_t*)0x2000029c = 0;
*(uint8_t*)0x2000029d = 0;
*(uint8_t*)0x2000029e = 0;
*(uint8_t*)0x2000029f = 0;
*(uint8_t*)0x200002a0 = 0;
*(uint8_t*)0x200002a1 = 0;
*(uint8_t*)0x200002a2 = 0;
*(uint8_t*)0x200002a3 = 0;
*(uint8_t*)0x200002a4 = 0;
*(uint8_t*)0x200002a5 = 0;
*(uint8_t*)0x200002a6 = 0;
*(uint8_t*)0x200002a7 = 0;
*(uint8_t*)0x200002a8 = 0;
*(uint8_t*)0x200002a9 = 0;
*(uint8_t*)0x200002aa = 0;
*(uint8_t*)0x200002ab = 0;
*(uint32_t*)0x200002ac = 0;
*(uint32_t*)0x200002b0 = -1;
*(uint32_t*)0x200002b4 = 0;
*(uint32_t*)0x200002b8 = 0;
*(uint32_t*)0x200002bc = 0;
res = syscall(__NR_bpf, 0ul, 0x20000280ul, 0x40ul);
if (res != -1)
r[0] = res;
*(uint64_t*)0x20000100 = 0;
*(uint64_t*)0x20000108 = 0;
*(uint64_t*)0x20000110 = 0x200002c0;
*(uint64_t*)0x20000118 = 0x20000000;
*(uint32_t*)0x20000120 = 0x1000;
*(uint32_t*)0x20000124 = r[0];
*(uint64_t*)0x20000128 = 0;
*(uint64_t*)0x20000130 = 0;
syscall(__NR_bpf, 0x1aul, 0x20000100ul, 0x38ul);

}
int main(void)
{
syscall(__NR_mmap, 0x1fff0000ul, 0x10000ul, 0ul, 0x32ul, -1, 0ul);
syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
syscall(__NR_mmap, 0x21000000ul, 0x10000ul, 0ul, 0x32ul, -1, 0ul);
for (procid = 0; procid < 16; procid++) {
if (fork() == 0) {
loop();
}
}
sleep(1000000);
return 0;
}




--
Alexey

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