memory leak in posix_clock_open
From: 柳菁峰
Date: Mon Mar 11 2024 - 04:12:36 EST
There is a memory leak in posix_clock_open,it was found by syzkaller when I tested it with linux-6.7(commit: 0dd3ee31125508cd67f7e7172247f05b7fd1753a).
When the ptp_open function (in driver/ptp/ptp.chardev. c) is called in posix_clock_open and the ptp_open function returns an error, it appears to crash, posix_clock_release has not been called to free pccontext.
Here is crash info:
BUG: memory leak
unreferenced object 0xffff8881065327c0 (size 16):
comm "syz-executor.7", pid 8994, jiffies 4295144661 (age 17.222s)
hex dump (first 16 bytes):
00 20 79 01 81 88 ff ff 00 00 00 00 00 00 00 00 . y.............
backtrace:
[<00000000fba736c4>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
[<00000000fba736c4>] slab_post_alloc_hook mm/slab.h:766 [inline]
[<00000000fba736c4>] slab_alloc_node mm/slub.c:3478 [inline]
[<00000000fba736c4>] __kmem_cache_alloc_node+0x1ee/0x250 mm/slub.c:3517
[<00000000f8fcb419>] kmalloc_trace+0x22/0xc0 mm/slab_common.c:1098
[<00000000afc910b4>] kmalloc include/linux/slab.h:600 [inline]
[<00000000afc910b4>] kzalloc include/linux/slab.h:721 [inline]
[<00000000afc910b4>] posix_clock_open+0xd3/0x250 kernel/time/posix-clock.c:126
[<00000000b1a43627>] chrdev_open+0x24b/0x6a0 fs/char_dev.c:414
[<00000000364febd5>] do_dentry_open+0x630/0x1580 fs/open.c:948
[<00000000ac62c8f4>] do_open fs/namei.c:3622 [inline]
[<00000000ac62c8f4>] path_openat+0x13f1/0x1c30 fs/namei.c:3779
[<0000000087bfc1bc>] do_filp_open+0x1c5/0x410 fs/namei.c:3809
[<0000000044db899a>] do_sys_openat2+0x139/0x190 fs/open.c:1437
[<00000000ee967f42>] do_sys_open fs/open.c:1452 [inline]
[<00000000ee967f42>] __do_sys_openat fs/open.c:1468 [inline]
[<00000000ee967f42>] __se_sys_openat fs/open.c:1463 [inline]
[<00000000ee967f42>] __x64_sys_openat+0x13d/0x1f0 fs/open.c:1463
[<000000004fad64b5>] do_syscall_x64 arch/x86/entry/common.c:52 [inline]
[<000000004fad64b5>] do_syscall_64+0x3e/0xf0 arch/x86/entry/common.c:83
[<00000000c2701c13>] entry_SYSCALL_64_after_hwframe+0x6e/0x76
BUG: leak checking failed
Here is the C code reproducer by syzkaller,It used inject fault to make ptp_open returns a error:
// autogenerated by syzkaller (https://github.com/google/syzkaller)
#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;
}
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 int inject_fault(int nth)
{
int fd;
fd = open("/proc/thread-self/fail-nth", O_RDWR);
if (fd == -1)
exit(1);
char buf[16];
sprintf(buf, "%d", nth);
if (write(fd, buf, strlen(buf)) != (ssize_t)strlen(buf))
exit(1);
return fd;
}
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 setup_fault()
{
static struct {
const char* file;
const char* val;
bool fatal;
} files[] = {
{"/sys/kernel/debug/failslab/ignore-gfp-wait", "N", true},
{"/sys/kernel/debug/fail_futex/ignore-private", "N", false},
{"/sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem", "N", false},
{"/sys/kernel/debug/fail_page_alloc/ignore-gfp-wait", "N", false},
{"/sys/kernel/debug/fail_page_alloc/min-order", "0", false},
};
unsigned i;
for (i = 0; i < sizeof(files) / sizeof(files[0]); i++) {
if (!write_file(files[i].file, files[i].val)) {
if (files[i].fatal)
exit(1);
}
}
}
#define KMEMLEAK_FILE "/sys/kernel/debug/kmemleak"
static void setup_leak()
{
if (!write_file(KMEMLEAK_FILE, "scan"))
exit(1);
sleep(5);
if (!write_file(KMEMLEAK_FILE, "scan"))
exit(1);
if (!write_file(KMEMLEAK_FILE, "clear"))
exit(1);
}
static void check_leaks(void)
{
int fd = open(KMEMLEAK_FILE, O_RDWR);
if (fd == -1)
exit(1);
uint64_t start = current_time_ms();
if (write(fd, "scan", 4) != 4)
exit(1);
sleep(1);
while (current_time_ms() - start < 4 * 1000)
sleep(1);
if (write(fd, "scan", 4) != 4)
exit(1);
static char buf[128 << 10];
ssize_t n = read(fd, buf, sizeof(buf) - 1);
if (n < 0)
exit(1);
int nleaks = 0;
if (n != 0) {
sleep(1);
if (write(fd, "scan", 4) != 4)
exit(1);
if (lseek(fd, 0, SEEK_SET) < 0)
exit(1);
n = read(fd, buf, sizeof(buf) - 1);
if (n < 0)
exit(1);
buf[n] = 0;
char* pos = buf;
char* end = buf + n;
while (pos < end) {
char* next = strstr(pos + 1, "unreferenced object");
if (!next)
next = end;
char prev = *next;
*next = 0;
fprintf(stderr, "BUG: memory leak\n%s\n", pos);
*next = prev;
pos = next;
nleaks++;
}
}
if (write(fd, "clear", 5) != 5)
exit(1);
close(fd);
if (nleaks)
exit(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;
}
check_leaks();
}
}
void execute_one(void)
{
memcpy((void*)0x20001180, "/dev/ptp0\000", 10);
inject_fault(7);
syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x20001180ul, /*flags=*/0ul, /*mode=*/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);
setup_leak();
setup_fault();
loop();
return 0;
}