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Date: Mon, 11 Mar 2024 17:46:09 +0800
From: Z qiang <qiang.zhang1211@...il.com>
To: 柳菁峰 <liujingfeng@...nxin.com>
Cc: "richardcochran@...il.com" <richardcochran@...il.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"syzkaller@...glegroups.com" <syzkaller@...glegroups.com>, "secalert@...hat.com" <secalert@...hat.com>
Subject: Re: memory leak in posix_clock_open
>
> 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
Hi, jingfeng
Please try the following modifications:
diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c
index 9de66bbbb3d1..71d9d8c394fa 100644
--- a/kernel/time/posix-clock.c
+++ b/kernel/time/posix-clock.c
@@ -137,6 +137,8 @@ static int posix_clock_open(struct inode *inode,
struct file *fp)
if (!err) {
get_device(clk->dev);
+ } else {
+ kfree(pccontext);
}
out:
up_read(&clk->rwsem);
Thanks
Zqiang
>
>
>
>
> 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;
> }
>
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