Re: [syzbot] [kernel?] general protection fault in joydev_connect

[xingwei lee]

Hi. I have reproduced this bug with repro.txt and repro.c below:

repro.txt
r0 = openat$uinput(0xffffffffffffff9c, &(0x7f0000000500), 0x802, 0x0)
ioctl$UI_DEV_SETUP(r0, 0x405c5503, &(0x7f0000000080)={{0x0, 0xffff,
0x3}, 'syz0\x00'})
ioctl$UI_DEV_CREATE(r0, 0x5501) (fail_nth: 51)

repro.c
#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);
}
}
}

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[1] = {0xffffffffffffffff};

void execute_one(void)
{
intptr_t res = 0;
memcpy((void*)0x20000500, "/dev/uinput\000", 12);
res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul,
/*file=*/0x20000500ul, /*flags=*/0x802ul, /*mode=*/0ul);
if (res != -1)
r[0] = res;
*(uint16_t*)0x20000080 = 0;
*(uint16_t*)0x20000082 = -1;
*(uint16_t*)0x20000084 = 3;
*(uint16_t*)0x20000086 = 0;
memcpy((void*)0x20000088,
"syz0\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000",
80);
*(uint32_t*)0x200000d8 = 0;
syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0x405c5503, /*arg=*/0x20000080ul);
inject_fault(51);
syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0x5501, 0);

}
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_fault();
loop();
return 0;
}