general protection fault in start_motor

[Dipanjan Das]

Hi,

We would like to report the following bug which has been found by our
modified version of syzkaller.

======================================================
description: general protection fault in start_motor
affected file: drivers/block/floppy.c
kernel version: 5.10.131
kernel commit: de62055f423f5dcb548f74cebd68f03c8903f73a
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=e49433cfed49b7d9
crash reproducer: attached
======================================================
Crash log:
======================================================
general protection fault, probably for non-canonical address
0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 8820 Comm: kworker/u4:48 Tainted: G           OE     5.10.131+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Workqueue: floppy fd_timer_workfn
RIP: 0010:start_motor+0x3a/0x3f0 drivers/block/floppy.c:1905
Code: 08 e8 4a 15 1c fd 48 8b 1d 03 30 4d 0b 48 b8 00 00 00 00 00 fc
ff df 0f b6 2d 72 22 4d 0b 48 89 da 48 c1 ea 03 89 e9 41 89 ed <0f> b6
04 02 83 e1 03 41 83 e5 03 84 c0 74 08 3c 03 0f 8e be 02 00
RSP: 0018:ffffc90000a47cc0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff845483d6 RDI: ffffffff84549f90
RBP: 0000000000000000 R08: ffff88803a2b1ac0 R09: fffffbfff19dad22
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff84549f90
R13: 0000000000000000 R14: ffff88810c148000 R15: ffff888100069800
FS:  0000000000000000(0000) GS:ffff88811a000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fb22000 CR3: 000000002daa9001 CR4: 0000000000170ef0
Call Trace:
 floppy_ready+0x7f/0x1950 drivers/block/floppy.c:1932
 process_one_work+0x953/0x15c0 kernel/workqueue.c:2279
 worker_thread+0x96/0xe20 kernel/workqueue.c:2425
 kthread+0x374/0x490 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
Modules linked in: uio_ivshmem(OE) uio(E)
---[ end trace 345300e45e5eb538 ]---
RIP: 0010:start_motor+0x3a/0x3f0 drivers/block/floppy.c:1905
Code: 08 e8 4a 15 1c fd 48 8b 1d 03 30 4d 0b 48 b8 00 00 00 00 00 fc
ff df 0f b6 2d 72 22 4d 0b 48 89 da 48 c1 ea 03 89 e9 41 89 ed <0f> b6
04 02 83 e1 03 41 83 e5 03 84 c0 74 08 3c 03 0f 8e be 02 00
RSP: 0018:ffffc90000a47cc0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff845483d6 RDI: ffffffff84549f90
RBP: 0000000000000000 R08: ffff88803a2b1ac0 R09: fffffbfff19dad22
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff84549f90
R13: 0000000000000000 R14: ffff88810c148000 R15: ffff888100069800
FS:  0000000000000000(0000) GS:ffff88811a000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fee2b352038 CR3: 00000000425db005 CR4: 0000000000170ef0
----------------
Code disassembly (best guess):
   0: 08 e8                or     %ch,%al
   2: 4a 15 1c fd 48 8b    rex.WX adc $0xffffffff8b48fd1c,%rax
   8: 1d 03 30 4d 0b        sbb    $0xb4d3003,%eax
   d: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
  14: fc ff df
  17: 0f b6 2d 72 22 4d 0b movzbl 0xb4d2272(%rip),%ebp        # 0xb4d2290
  1e: 48 89 da              mov    %rbx,%rdx
  21: 48 c1 ea 03          shr    $0x3,%rdx
  25: 89 e9                mov    %ebp,%ecx
  27: 41 89 ed              mov    %ebp,%r13d
* 2a: 0f b6 04 02          movzbl (%rdx,%rax,1),%eax <-- trapping instruction
  2e: 83 e1 03              and    $0x3,%ecx
  31: 41 83 e5 03          and    $0x3,%r13d
  35: 84 c0                test   %al,%al
  37: 74 08                je     0x41
  39: 3c 03                cmp    $0x3,%al
  3b: 0f                    .byte 0xf
  3c: 8e                    .byte 0x8e
  3d: be                    .byte 0xbe
  3e: 02 00                add    (%rax),%al

-- 
Thanks and Regards,

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

#define _GNU_SOURCE 

#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.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>

#include <linux/futex.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 void thread_start(void* (*fn)(void*), void* arg)
{
	pthread_t th;
	pthread_attr_t attr;
	pthread_attr_init(&attr);
	pthread_attr_setstacksize(&attr, 128 << 10);
	int i = 0;
	for (; i < 100; i++) {
		if (pthread_create(&th, &attr, fn, arg) == 0) {
			pthread_attr_destroy(&attr);
			return;
		}
		if (errno == EAGAIN) {
			usleep(50);
			continue;
		}
		break;
	}
	exit(1);
}

typedef struct {
	int state;
} event_t;

static void event_init(event_t* ev)
{
	ev->state = 0;
}

static void event_reset(event_t* ev)
{
	ev->state = 0;
}

static void event_set(event_t* ev)
{
	if (ev->state)
	exit(1);
	__atomic_store_n(&ev->state, 1, __ATOMIC_RELEASE);
	syscall(SYS_futex, &ev->state, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1000000);
}

static void event_wait(event_t* ev)
{
	while (!__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
		syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, 0);
}

static int event_isset(event_t* ev)
{
	return __atomic_load_n(&ev->state, __ATOMIC_ACQUIRE);
}

static int event_timedwait(event_t* ev, uint64_t timeout)
{
	uint64_t start = current_time_ms();
	uint64_t now = start;
	for (;;) {
		uint64_t remain = timeout - (now - start);
		struct timespec ts;
		ts.tv_sec = remain / 1000;
		ts.tv_nsec = (remain % 1000) * 1000 * 1000;
		syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, &ts);
		if (__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
			return 1;
		now = current_time_ms();
		if (now - start > timeout)
			return 0;
	}
}

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 long syz_open_dev(volatile long a0, volatile long a1, volatile long a2)
{
	if (a0 == 0xc || a0 == 0xb) {
		char buf[128];
		sprintf(buf, "/dev/%s/%d:%d", a0 == 0xc ? "char" : "block", (uint8_t)a1, (uint8_t)a2);
		return open(buf, O_RDWR, 0);
	} else {
		char buf[1024];
		char* hash;
		strncpy(buf, (char*)a0, sizeof(buf) - 1);
		buf[sizeof(buf) - 1] = 0;
		while ((hash = strchr(buf, '#'))) {
			*hash = '0' + (char)(a1 % 10);
			a1 /= 10;
		}
		return open(buf, a2, 0);
	}
}

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");
}

struct thread_t {
	int created, call;
	event_t ready, done;
};

static struct thread_t threads[16];
static void execute_call(int call);
static int running;

static void* thr(void* arg)
{
	struct thread_t* th = (struct thread_t*)arg;
	for (;;) {
		event_wait(&th->ready);
		event_reset(&th->ready);
		execute_call(th->call);
		__atomic_fetch_sub(&running, 1, __ATOMIC_RELAXED);
		event_set(&th->done);
	}
	return 0;
}

static void execute_one(void)
{
	int i, call, thread;
	for (call = 0; call < 10; call++) {
		for (thread = 0; thread < (int)(sizeof(threads) / sizeof(threads[0])); thread++) {
			struct thread_t* th = &threads[thread];
			if (!th->created) {
				th->created = 1;
				event_init(&th->ready);
				event_init(&th->done);
				event_set(&th->done);
				thread_start(thr, th);
			}
			if (!event_isset(&th->done))
				continue;
			event_reset(&th->done);
			th->call = call;
			__atomic_fetch_add(&running, 1, __ATOMIC_RELAXED);
			event_set(&th->ready);
			if (call == 3 || call == 4 || call == 5 || call == 6)
				break;
			event_timedwait(&th->done, 50);
			break;
		}
	}
	for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++)
		sleep_ms(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_call(int call)
{
		intptr_t res = 0;
	switch (call) {
	case 0:
*(uint16_t*)0x20000040 = 2;
*(uint16_t*)0x20000042 = htobe16(0x4e20);
*(uint32_t*)0x20000044 = htobe32(0);
*(uint8_t*)0x200000c0 = 0;
*(uint8_t*)0x200000c1 = 0;
*(uint16_t*)0x200000c2 = 0x34;
*(uint32_t*)0x200000c4 = 0;
memcpy((void*)0x200000c8, "\x4b\x2f\x09\xfc\x47\x61\xb8\x60\xe6\x7f\xe9\x46\xd3\x73\x42\xa7\x1e\x0b\xbe\xe0\xb2\x52\x00\x1f\x8e\x09\xf2\xa4\x0b\x5f\x06\x45\x81\x5e\x6c\xea\xae\x84\x7a\x7f\x50\xa3\xb3\xeb\x07\x7d\x95\x11\x50\x2c\xee\x3d\xee\xdf\xc9\x30\xe6\x6a\x46\x9d\x4e\x88\xcd\x1c\x66\x70\x55\xd0\x7f\x9e\xf9\x5f\x0d\xd1\xd2\x42\x6a\x97\xf5\xed", 80);
		syscall(__NR_setsockopt, -1, 6, 0xe, 0x20000040ul, 0xd8ul);
		break;
	case 1:
memcpy((void*)0x200001c0, "/dev/fd#\000", 9);
		res = -1;
res = syz_open_dev(0x200001c0, 0, 3);
		if (res != -1)
				r[0] = res;
		break;
	case 2:
		syscall(__NR_ioctl, r[0], 0x241, 0);
		break;
	case 3:
*(uint16_t*)0x20000040 = 2;
*(uint16_t*)0x20000042 = htobe16(0x4e20);
*(uint32_t*)0x20000044 = htobe32(0);
*(uint8_t*)0x200000c0 = 0;
*(uint8_t*)0x200000c1 = 0;
*(uint16_t*)0x200000c2 = 0x34;
*(uint32_t*)0x200000c4 = 0;
memcpy((void*)0x200000c8, "\x4b\x2f\x09\xfc\x47\x61\xb8\x60\xe6\x7f\xe9\x46\xd3\x73\x42\xa7\x1e\x0b\xbe\xe0\xb2\x52\x00\x1f\x8e\x09\xf2\xa4\x0b\x5f\x06\x45\x81\x5e\x6c\xea\xae\x84\x7a\x7f\x50\xa3\xb3\xeb\x07\x7d\x95\x11\x50\x2c\xee\x3d\xee\xdf\xc9\x30\xe6\x6a\x46\x9d\x4e\x88\xcd\x1c\x66\x70\x55\xd0\x7f\x9e\xf9\x5f\x0d\xd1\xd2\x42\x6a\x97\xf5\xed", 80);
		syscall(__NR_setsockopt, -1, 6, 0xe, 0x20000040ul, 0xd8ul);
		break;
	case 4:
memcpy((void*)0x20000000, "/dev/fd#\000", 9);
syz_open_dev(0x20000000, -1, 0x4000);
		break;
	case 5:
		syscall(__NR_ioctl, r[0], 0x241, 0);
		break;
	case 6:
		syscall(__NR_ioctl, r[0], 0x247, 0);
		break;
	case 7:
syz_open_dev(0, 8, 0x200);
		break;
	case 8:
*(uint32_t*)0x20000180 = 2;
		syscall(__NR_setsockopt, -1, 6, 0x14, 0x20000180ul, 4ul);
		break;
	case 9:
		syscall(__NR_ioctl, r[0], 0x247, 0);
		break;
	}

}
int main(void)
{
		syscall(__NR_mmap, 0x1ffff000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
	syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
	syscall(__NR_mmap, 0x21000000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
	for (procid = 0; procid < 8; procid++) {
		if (fork() == 0) {
			loop();
		}
	}
	sleep(1000000);
	return 0;
}

Attachment: repro.syz
Description: Binary data