* Re: [PATCH] drivers: firmware_loader: fix race between sysfs fallback cleanup and device removal
2026-04-21 14:14 ` Greg KH
@ 2026-04-22 11:36 ` Li Zao
2026-04-22 11:52 ` Greg KH
0 siblings, 1 reply; 4+ messages in thread
From: Li Zao @ 2026-04-22 11:36 UTC (permalink / raw)
To: Greg KH; +Cc: mcgrof, russ.weight, rafael, linux-kernel
In the report, I saw:
sysfs group 'power' not found for kobject 'ueagle-atm!eagleI.fw'
WARNING: CPU: 0 PID: 14408 at fs/sysfs/group.c:282 sysfs_remove_group
fs/sysfs/group.c:282 [inline]
WARNING: CPU: 0 PID: 14408 at fs/sysfs/group.c:282
sysfs_remove_group+0x159/0x1b0 fs/sysfs/group.c:273
The reproducer mainly runs an infinite loop(), which continuously forks
and executes execute_one() within loop(). execute_one() constructs
parameters and calls syz_usb_connect(), causing a large number of
connect and disconnect calls.
According to the call trace, this problem is triggered when
firmware_fallback_sysfs() calls device_del(). So I suppose the problem
is likely caused by a large number of connect/disconnect operations
triggering some kind of race condition, leading to the device being
unregistered and ultimately causing sysfs_remove_group() to remove
an object that no longer exists. But to be honest, since I'm not very
familiar with this code, I can't be 100% sure. Sorry for my lack of rigor.
As for the "out:" line issue, it is indeed a bit strange; I will clean it up in
the next submission.
The complete C reproducer is attached below:
#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 <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mount.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/usb/ch9.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;
}
#define MAX_FDS 30
#define USB_MAX_IFACE_NUM 4
#define USB_MAX_EP_NUM 32
#define USB_MAX_FDS 6
struct usb_endpoint_index {
struct usb_endpoint_descriptor desc;
int handle;
};
struct usb_iface_index {
struct usb_interface_descriptor* iface;
uint8_t bInterfaceNumber;
uint8_t bAlternateSetting;
uint8_t bInterfaceClass;
struct usb_endpoint_index eps[USB_MAX_EP_NUM];
int eps_num;
};
struct usb_device_index {
struct usb_device_descriptor* dev;
struct usb_config_descriptor* config;
uint8_t bDeviceClass;
uint8_t bMaxPower;
int config_length;
struct usb_iface_index ifaces[USB_MAX_IFACE_NUM];
int ifaces_num;
int iface_cur;
};
struct usb_info {
int fd;
struct usb_device_index index;
};
static struct usb_info usb_devices[USB_MAX_FDS];
static struct usb_device_index* lookup_usb_index(int fd)
{
for (int i = 0; i < USB_MAX_FDS; i++) {
if (__atomic_load_n(&usb_devices[i].fd, __ATOMIC_ACQUIRE) == fd)
return &usb_devices[i].index;
}
return NULL;
}
static int usb_devices_num;
static bool parse_usb_descriptor(const char* buffer, size_t length,
struct usb_device_index* index)
{
if (length < sizeof(*index->dev) + sizeof(*index->config))
return false;
memset(index, 0, sizeof(*index));
index->dev = (struct usb_device_descriptor*)buffer;
index->config = (struct usb_config_descriptor*)(buffer + sizeof(*index->dev));
index->bDeviceClass = index->dev->bDeviceClass;
index->bMaxPower = index->config->bMaxPower;
index->config_length = length - sizeof(*index->dev);
index->iface_cur = -1;
size_t offset = 0;
while (true) {
if (offset + 1 >= length)
break;
uint8_t desc_length = buffer[offset];
uint8_t desc_type = buffer[offset + 1];
if (desc_length <= 2)
break;
if (offset + desc_length > length)
break;
if (desc_type == USB_DT_INTERFACE &&
index->ifaces_num < USB_MAX_IFACE_NUM) {
struct usb_interface_descriptor* iface =
(struct usb_interface_descriptor*)(buffer + offset);
index->ifaces[index->ifaces_num].iface = iface;
index->ifaces[index->ifaces_num].bInterfaceNumber =
iface->bInterfaceNumber;
index->ifaces[index->ifaces_num].bAlternateSetting =
iface->bAlternateSetting;
index->ifaces[index->ifaces_num].bInterfaceClass = iface->bInterfaceClass;
index->ifaces_num++;
}
if (desc_type == USB_DT_ENDPOINT && index->ifaces_num > 0) {
struct usb_iface_index* iface = &index->ifaces[index->ifaces_num - 1];
if (iface->eps_num < USB_MAX_EP_NUM) {
memcpy(&iface->eps[iface->eps_num].desc, buffer + offset,
sizeof(iface->eps[iface->eps_num].desc));
iface->eps_num++;
}
}
offset += desc_length;
}
return true;
}
static struct usb_device_index* add_usb_index(int fd, const char* dev,
size_t dev_len)
{
int i = __atomic_fetch_add(&usb_devices_num, 1, __ATOMIC_RELAXED);
if (i >= USB_MAX_FDS)
return NULL;
if (!parse_usb_descriptor(dev, dev_len, &usb_devices[i].index))
return NULL;
__atomic_store_n(&usb_devices[i].fd, fd, __ATOMIC_RELEASE);
return &usb_devices[i].index;
}
struct vusb_connect_string_descriptor {
uint32_t len;
char* str;
} __attribute__((packed));
struct vusb_connect_descriptors {
uint32_t qual_len;
char* qual;
uint32_t bos_len;
char* bos;
uint32_t strs_len;
struct vusb_connect_string_descriptor strs[0];
} __attribute__((packed));
static const char default_string[] = {8, USB_DT_STRING, 's', 0, 'y', 0, 'z', 0};
static const char default_lang_id[] = {4, USB_DT_STRING, 0x09, 0x04};
static bool
lookup_connect_response_in(int fd, const struct vusb_connect_descriptors* descs,
const struct usb_ctrlrequest* ctrl,
struct usb_qualifier_descriptor* qual,
char** response_data, uint32_t* response_length)
{
struct usb_device_index* index = lookup_usb_index(fd);
uint8_t str_idx;
if (!index)
return false;
switch (ctrl->bRequestType & USB_TYPE_MASK) {
case USB_TYPE_STANDARD:
switch (ctrl->bRequest) {
case USB_REQ_GET_DESCRIPTOR:
switch (ctrl->wValue >> 8) {
case USB_DT_DEVICE:
*response_data = (char*)index->dev;
*response_length = sizeof(*index->dev);
return true;
case USB_DT_CONFIG:
*response_data = (char*)index->config;
*response_length = index->config_length;
return true;
case USB_DT_STRING:
str_idx = (uint8_t)ctrl->wValue;
if (descs && str_idx < descs->strs_len) {
*response_data = descs->strs[str_idx].str;
*response_length = descs->strs[str_idx].len;
return true;
}
if (str_idx == 0) {
*response_data = (char*)&default_lang_id[0];
*response_length = default_lang_id[0];
return true;
}
*response_data = (char*)&default_string[0];
*response_length = default_string[0];
return true;
case USB_DT_BOS:
*response_data = descs->bos;
*response_length = descs->bos_len;
return true;
case USB_DT_DEVICE_QUALIFIER:
if (!descs->qual) {
qual->bLength = sizeof(*qual);
qual->bDescriptorType = USB_DT_DEVICE_QUALIFIER;
qual->bcdUSB = index->dev->bcdUSB;
qual->bDeviceClass = index->dev->bDeviceClass;
qual->bDeviceSubClass = index->dev->bDeviceSubClass;
qual->bDeviceProtocol = index->dev->bDeviceProtocol;
qual->bMaxPacketSize0 = index->dev->bMaxPacketSize0;
qual->bNumConfigurations = index->dev->bNumConfigurations;
qual->bRESERVED = 0;
*response_data = (char*)qual;
*response_length = sizeof(*qual);
return true;
}
*response_data = descs->qual;
*response_length = descs->qual_len;
return true;
default:
break;
}
break;
default:
break;
}
break;
default:
break;
}
return false;
}
typedef bool (*lookup_connect_out_response_t)(
int fd, const struct vusb_connect_descriptors* descs,
const struct usb_ctrlrequest* ctrl, bool* done);
static bool lookup_connect_response_out_generic(
int fd, const struct vusb_connect_descriptors* descs,
const struct usb_ctrlrequest* ctrl, bool* done)
{
switch (ctrl->bRequestType & USB_TYPE_MASK) {
case USB_TYPE_STANDARD:
switch (ctrl->bRequest) {
case USB_REQ_SET_CONFIGURATION:
*done = true;
return true;
default:
break;
}
break;
}
return false;
}
#define UDC_NAME_LENGTH_MAX 128
struct usb_raw_init {
__u8 driver_name[UDC_NAME_LENGTH_MAX];
__u8 device_name[UDC_NAME_LENGTH_MAX];
__u8 speed;
};
enum usb_raw_event_type {
USB_RAW_EVENT_INVALID = 0,
USB_RAW_EVENT_CONNECT = 1,
USB_RAW_EVENT_CONTROL = 2,
};
struct usb_raw_event {
__u32 type;
__u32 length;
__u8 data[0];
};
struct usb_raw_ep_io {
__u16 ep;
__u16 flags;
__u32 length;
__u8 data[0];
};
#define USB_RAW_EPS_NUM_MAX 30
#define USB_RAW_EP_NAME_MAX 16
#define USB_RAW_EP_ADDR_ANY 0xff
struct usb_raw_ep_caps {
__u32 type_control : 1;
__u32 type_iso : 1;
__u32 type_bulk : 1;
__u32 type_int : 1;
__u32 dir_in : 1;
__u32 dir_out : 1;
};
struct usb_raw_ep_limits {
__u16 maxpacket_limit;
__u16 max_streams;
__u32 reserved;
};
struct usb_raw_ep_info {
__u8 name[USB_RAW_EP_NAME_MAX];
__u32 addr;
struct usb_raw_ep_caps caps;
struct usb_raw_ep_limits limits;
};
struct usb_raw_eps_info {
struct usb_raw_ep_info eps[USB_RAW_EPS_NUM_MAX];
};
#define USB_RAW_IOCTL_INIT _IOW('U', 0, struct usb_raw_init)
#define USB_RAW_IOCTL_RUN _IO('U', 1)
#define USB_RAW_IOCTL_EVENT_FETCH _IOR('U', 2, struct usb_raw_event)
#define USB_RAW_IOCTL_EP0_WRITE _IOW('U', 3, struct usb_raw_ep_io)
#define USB_RAW_IOCTL_EP0_READ _IOWR('U', 4, struct usb_raw_ep_io)
#define USB_RAW_IOCTL_EP_ENABLE _IOW('U', 5, struct usb_endpoint_descriptor)
#define USB_RAW_IOCTL_EP_DISABLE _IOW('U', 6, __u32)
#define USB_RAW_IOCTL_EP_WRITE _IOW('U', 7, struct usb_raw_ep_io)
#define USB_RAW_IOCTL_EP_READ _IOWR('U', 8, struct usb_raw_ep_io)
#define USB_RAW_IOCTL_CONFIGURE _IO('U', 9)
#define USB_RAW_IOCTL_VBUS_DRAW _IOW('U', 10, __u32)
#define USB_RAW_IOCTL_EPS_INFO _IOR('U', 11, struct usb_raw_eps_info)
#define USB_RAW_IOCTL_EP0_STALL _IO('U', 12)
#define USB_RAW_IOCTL_EP_SET_HALT _IOW('U', 13, __u32)
#define USB_RAW_IOCTL_EP_CLEAR_HALT _IOW('U', 14, __u32)
#define USB_RAW_IOCTL_EP_SET_WEDGE _IOW('U', 15, __u32)
static int usb_raw_open()
{
return open("/dev/raw-gadget", O_RDWR);
}
static int usb_raw_init(int fd, uint32_t speed, const char* driver,
const char* device)
{
struct usb_raw_init arg;
strncpy((char*)&arg.driver_name[0], driver, sizeof(arg.driver_name));
strncpy((char*)&arg.device_name[0], device, sizeof(arg.device_name));
arg.speed = speed;
return ioctl(fd, USB_RAW_IOCTL_INIT, &arg);
}
static int usb_raw_run(int fd)
{
return ioctl(fd, USB_RAW_IOCTL_RUN, 0);
}
static int usb_raw_configure(int fd)
{
return ioctl(fd, USB_RAW_IOCTL_CONFIGURE, 0);
}
static int usb_raw_vbus_draw(int fd, uint32_t power)
{
return ioctl(fd, USB_RAW_IOCTL_VBUS_DRAW, power);
}
static int usb_raw_ep0_write(int fd, struct usb_raw_ep_io* io)
{
return ioctl(fd, USB_RAW_IOCTL_EP0_WRITE, io);
}
static int usb_raw_ep0_read(int fd, struct usb_raw_ep_io* io)
{
return ioctl(fd, USB_RAW_IOCTL_EP0_READ, io);
}
static int usb_raw_event_fetch(int fd, struct usb_raw_event* event)
{
return ioctl(fd, USB_RAW_IOCTL_EVENT_FETCH, event);
}
static int usb_raw_ep_enable(int fd, struct usb_endpoint_descriptor* desc)
{
return ioctl(fd, USB_RAW_IOCTL_EP_ENABLE, desc);
}
static int usb_raw_ep_disable(int fd, int ep)
{
return ioctl(fd, USB_RAW_IOCTL_EP_DISABLE, ep);
}
static int usb_raw_ep0_stall(int fd)
{
return ioctl(fd, USB_RAW_IOCTL_EP0_STALL, 0);
}
#define USB_MAX_PACKET_SIZE 4096
struct usb_raw_control_event {
struct usb_raw_event inner;
struct usb_ctrlrequest ctrl;
char data[USB_MAX_PACKET_SIZE];
};
struct usb_raw_ep_io_data {
struct usb_raw_ep_io inner;
char data[USB_MAX_PACKET_SIZE];
};
static void set_interface(int fd, int n)
{
struct usb_device_index* index = lookup_usb_index(fd);
if (!index)
return;
if (index->iface_cur >= 0 && index->iface_cur < index->ifaces_num) {
for (int ep = 0; ep < index->ifaces[index->iface_cur].eps_num; ep++) {
int rv = usb_raw_ep_disable(
fd, index->ifaces[index->iface_cur].eps[ep].handle);
if (rv < 0) {
} else {
}
}
}
if (n >= 0 && n < index->ifaces_num) {
for (int ep = 0; ep < index->ifaces[n].eps_num; ep++) {
int rv = usb_raw_ep_enable(fd, &index->ifaces[n].eps[ep].desc);
if (rv < 0) {
} else {
index->ifaces[n].eps[ep].handle = rv;
}
}
index->iface_cur = n;
}
}
static int configure_device(int fd)
{
struct usb_device_index* index = lookup_usb_index(fd);
if (!index)
return -1;
int rv = usb_raw_vbus_draw(fd, index->bMaxPower);
if (rv < 0) {
return rv;
}
rv = usb_raw_configure(fd);
if (rv < 0) {
return rv;
}
set_interface(fd, 0);
return 0;
}
static volatile long
syz_usb_connect_impl(uint64_t speed, uint64_t dev_len, const char* dev,
const struct vusb_connect_descriptors* descs,
lookup_connect_out_response_t lookup_connect_response_out)
{
if (!dev) {
return -1;
}
int fd = usb_raw_open();
if (fd < 0) {
return fd;
}
if (fd >= MAX_FDS) {
close(fd);
return -1;
}
struct usb_device_index* index = add_usb_index(fd, dev, dev_len);
if (!index) {
return -1;
}
char device[32];
sprintf(&device[0], "dummy_udc.%llu", procid);
int rv = usb_raw_init(fd, speed, "dummy_udc", &device[0]);
if (rv < 0) {
return rv;
}
rv = usb_raw_run(fd);
if (rv < 0) {
return rv;
}
bool done = false;
while (!done) {
struct usb_raw_control_event event;
event.inner.type = 0;
event.inner.length = sizeof(event.ctrl);
rv = usb_raw_event_fetch(fd, (struct usb_raw_event*)&event);
if (rv < 0) {
return rv;
}
if (event.inner.type != USB_RAW_EVENT_CONTROL)
continue;
char* response_data = NULL;
uint32_t response_length = 0;
struct usb_qualifier_descriptor qual;
if (event.ctrl.bRequestType & USB_DIR_IN) {
if (!lookup_connect_response_in(fd, descs, &event.ctrl, &qual,
&response_data, &response_length)) {
usb_raw_ep0_stall(fd);
continue;
}
} else {
if (!lookup_connect_response_out(fd, descs, &event.ctrl, &done)) {
usb_raw_ep0_stall(fd);
continue;
}
response_data = NULL;
response_length = event.ctrl.wLength;
}
if ((event.ctrl.bRequestType & USB_TYPE_MASK) == USB_TYPE_STANDARD &&
event.ctrl.bRequest == USB_REQ_SET_CONFIGURATION) {
rv = configure_device(fd);
if (rv < 0) {
return rv;
}
}
struct usb_raw_ep_io_data response;
response.inner.ep = 0;
response.inner.flags = 0;
if (response_length > sizeof(response.data))
response_length = 0;
if (event.ctrl.wLength < response_length)
response_length = event.ctrl.wLength;
response.inner.length = response_length;
if (response_data)
memcpy(&response.data[0], response_data, response_length);
else
memset(&response.data[0], 0, response_length);
if (event.ctrl.bRequestType & USB_DIR_IN) {
rv = usb_raw_ep0_write(fd, (struct usb_raw_ep_io*)&response);
} else {
rv = usb_raw_ep0_read(fd, (struct usb_raw_ep_io*)&response);
}
if (rv < 0) {
return rv;
}
}
sleep_ms(200);
return fd;
}
static volatile long syz_usb_connect(volatile long a0, volatile long a1,
volatile long a2, volatile long a3)
{
uint64_t speed = a0;
uint64_t dev_len = a1;
const char* dev = (const char*)a2;
const struct vusb_connect_descriptors* descs =
(const struct vusb_connect_descriptors*)a3;
return syz_usb_connect_impl(speed, dev_len, dev, descs,
&lookup_connect_response_out_generic);
}
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 (;;) {
sleep_ms(10);
if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
break;
if (current_time_ms() - start < 5000)
continue;
kill_and_wait(pid, &status);
break;
}
}
}
void execute_one(void)
{
if (write(1, "executing program\n", sizeof("executing program\n") - 1)) {
}
// syz_usb_connect arguments: [
// speed: usb_device_speed = 0x3 (8 bytes)
// dev_len: len = 0x24 (8 bytes)
// dev: ptr[in, usb_device_descriptor] {
// usb_device_descriptor {
// inner: usb_device_descriptor_verbose_t[flags[usb_versions, int16],
// 0, 0, 0, flags[usb_device_max_packet_sizes, int8], 0, 0, 0,
// array[usb_config_descriptor, 1]] {
// bLength: const = 0x12 (1 bytes)
// bDescriptorType: const = 0x1 (1 bytes)
// bcdUSB: usb_versions = 0x0 (2 bytes)
// bDeviceClass: const = 0x1 (1 bytes)
// bDeviceSubClass: const = 0x6e (1 bytes)
// bDeviceProtocol: const = 0x80 (1 bytes)
// bMaxPacketSize0: usb_device_max_packet_sizes = 0x8 (1 bytes)
// idVendor: const = 0x1039 (2 bytes)
// idProduct: const = 0x2131 (2 bytes)
// bcdDevice: const = 0xb4c6 (2 bytes)
// iManufacturer: const = 0x0 (1 bytes)
// iProduct: const = 0x0 (1 bytes)
// iSerialNumber: const = 0x0 (1 bytes)
// bNumConfigurations: len = 0x1 (1 bytes)
// configs: array[usb_config_descriptor] {
// usb_config_descriptor {
// inner: usb_config_descriptor_verbose_t[int8, len[interfaces,
// int8], int8, flags[usb_config_attributes, int8], int8,
// array[usb_interface_descriptor, 1:4]] {
// bLength: const = 0x9 (1 bytes)
// bDescriptorType: const = 0x2 (1 bytes)
// wTotalLength: len = 0x12 (2 bytes)
// bNumInterfaces: len = 0x1 (1 bytes)
// bConfigurationValue: int8 = 0x9 (1 bytes)
// iConfiguration: int8 = 0x0 (1 bytes)
// bmAttributes: usb_config_attributes = 0x1c0 (1 bytes)
// bMaxPower: int8 = 0x0 (1 bytes)
// interfaces: array[usb_interface_descriptor] {
// usb_interface_descriptor {
// inner: usb_interface_descriptor_verbose_t[int8, int8,
// len[endpoints, int8], const[0, int8], const[0, int8],
// const[0, int8], int8,
// array[usb_interface_extra_descriptor, 0:2],
// array[usb_endpoint_descriptor, 0:16]] {
// bLength: const = 0x9 (1 bytes)
// bDescriptorType: const = 0x4 (1 bytes)
// bInterfaceNumber: int8 = 0x7e (1 bytes)
// bAlternateSetting: int8 = 0x8 (1 bytes)
// bNumEndpoints: len = 0x0 (1 bytes)
// bInterfaceClass: const = 0x5d (1 bytes)
// bInterfaceSubClass: const = 0x1e (1 bytes)
// bInterfaceProtocol: const = 0xfc (1 bytes)
// iInterface: int8 = 0x0 (1 bytes)
// extra: array[usb_interface_extra_descriptor] {
// }
// endpoints: array[usb_endpoint_descriptor] {
// }
// }
// }
// }
// }
// }
// }
// }
// }
// }
// conn_descs: nil
// ]
// returns fd_usb
*(uint8_t*)0x200000000140 = 0x12;
*(uint8_t*)0x200000000141 = 1;
*(uint16_t*)0x200000000142 = 0;
*(uint8_t*)0x200000000144 = 1;
*(uint8_t*)0x200000000145 = 0x6e;
*(uint8_t*)0x200000000146 = 0x80;
*(uint8_t*)0x200000000147 = 8;
*(uint16_t*)0x200000000148 = 0x1039;
*(uint16_t*)0x20000000014a = 0x2131;
*(uint16_t*)0x20000000014c = 0xb4c6;
*(uint8_t*)0x20000000014e = 0;
*(uint8_t*)0x20000000014f = 0;
*(uint8_t*)0x200000000150 = 0;
*(uint8_t*)0x200000000151 = 1;
*(uint8_t*)0x200000000152 = 9;
*(uint8_t*)0x200000000153 = 2;
*(uint16_t*)0x200000000154 = 0x12;
*(uint8_t*)0x200000000156 = 1;
*(uint8_t*)0x200000000157 = 9;
*(uint8_t*)0x200000000158 = 0;
*(uint8_t*)0x200000000159 = 0xc0;
*(uint8_t*)0x20000000015a = 0;
*(uint8_t*)0x20000000015b = 9;
*(uint8_t*)0x20000000015c = 4;
*(uint8_t*)0x20000000015d = 0x7e;
*(uint8_t*)0x20000000015e = 8;
*(uint8_t*)0x20000000015f = 0;
*(uint8_t*)0x200000000160 = 0x5d;
*(uint8_t*)0x200000000161 = 0x1e;
*(uint8_t*)0x200000000162 = 0xfc;
*(uint8_t*)0x200000000163 = 0;
syz_usb_connect(/*speed=USB_SPEED_HIGH*/ 3, /*dev_len=*/0x24,
/*dev=*/0x200000000140, /*conn_descs=*/0);
}
int main(void)
{
syscall(__NR_mmap, /*addr=*/0x1ffffffff000ul, /*len=*/0x1000ul, /*prot=*/0ul,
/*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul,
/*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200000000000ul, /*len=*/0x1000000ul,
/*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/ 7ul,
/*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul,
/*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200001000000ul, /*len=*/0x1000ul, /*prot=*/0ul,
/*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul,
/*fd=*/(intptr_t)-1, /*offset=*/0ul);
const char* reason;
(void)reason;
loop();
return 0;
}
Best regards,
Haocheng
On Tue, Apr 21, 2026 at 10:14 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Apr 21, 2026 at 09:49:57PM +0800, l1za0.sec@gmail.com wrote:
> > From: Haocheng Yu <l1za0.sec@gmail.com>
> >
> > A WARNING in firmware_fallback_sysfs is reported by a modified
> > Syzkaller-based kernel fuzzing tool that we developed.
> >
> > The cause of this issue is a possible race condition between
> > firmware sysfs fallback cleanup and hot-plug or other device
> > lifecycle paths.
>
> How exactly? This device is under full control of this function, it
> should "know" if it is registered or not. No other code path should be
> ever unregistering it.
>
> > In this case, fw_load_sysfs_fallback() might run cleanup after the
> > fallback device has already been removed, i.e., it would execute
> > device_del(), then dpm_sysfs_remove(), and finally trigger a
> > warning in sysfs_remove_group().
>
> How exactly does that happen?
>
> > This problem can be avoided by adding device_is_registered()
> > check before calling device_del().
> >
> > Signed-off-by: Haocheng Yu <l1za0.sec@gmail.com>
>
> Do you have a reproducer for this issue?
>
>
> > ---
> > drivers/base/firmware_loader/fallback.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
> > index bf68e3947814..a8d8c494f82d 100644
> > --- a/drivers/base/firmware_loader/fallback.c
> > +++ b/drivers/base/firmware_loader/fallback.c
> > @@ -116,8 +116,9 @@ static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs, long timeout)
> > } else if (fw_priv->is_paged_buf && !fw_priv->data)
> > retval = -ENOMEM;
> >
> > -out:
> > - device_del(f_dev);
> > +out:
> > + if (device_is_registered(f_dev))
> > + device_del(f_dev);
>
> Again, this feels wrong. And why was the "out:" line added and added
> back? That feels like something is odd with the diff?
>
> thanks,
>
> greg k-h
^ permalink raw reply [flat|nested] 4+ messages in thread