From: Peter Hutterer peter.hutterer@who-t.net
There is a need for userspace applications to open HID devices directly. Use-cases include configuration of gaming mice or direct access to joystick devices. The latter is currently handled by the uaccess tag in systemd, other devices include more custom/local configurations or just sudo.
A better approach is what we already have for evdev devices: give the application a file descriptor and revoke it when it may no longer access that device.
This patch is the hidraw equivalent to the EVIOCREVOKE ioctl, see commit c7dc65737c9a ("Input: evdev - add EVIOCREVOKE ioctl") for full details.
An MR for systemd-logind has been filed here: https://github.com/systemd/systemd/pull/33970
Signed-off-by: Peter Hutterer peter.hutterer@who-t.net Signed-off-by: Benjamin Tissoires bentiss@kernel.org
---
First version of the patch: https://patchwork.kernel.org/project/linux-input/patch/YmEAPZKDisM2HAsG@quok...
Changes to v1: - add the hidraw_is_revoked and hidraw_open_errno weak functions as suggested by Benjamin
Changes to v2: - use __bpf_hook_start/end to silence compiler warnings (see kernel test bot)
Changes to v3 (bentiss): - drop the BPF related changes, the API is not clear ATM, and it's wrong in v2, as ERROR_INJECTION should not be used for normal fmodret. - drop hidraw_open_errno() new function. The API seems interesting, but nothing is really ready, so let's not add a useless API for nothing.
Changes to v4: none --- drivers/hid/hidraw.c | 39 +++++++++++++++++++++++++++++++++++---- include/linux/hidraw.h | 1 + include/uapi/linux/hidraw.h | 1 + 3 files changed, 37 insertions(+), 4 deletions(-)
diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c index 716294e40e8a..c887f48756f4 100644 --- a/drivers/hid/hidraw.c +++ b/drivers/hid/hidraw.c @@ -38,12 +38,20 @@ static const struct class hidraw_class = { static struct hidraw *hidraw_table[HIDRAW_MAX_DEVICES]; static DECLARE_RWSEM(minors_rwsem);
+static inline bool hidraw_is_revoked(struct hidraw_list *list) +{ + return list->revoked; +} + static ssize_t hidraw_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos) { struct hidraw_list *list = file->private_data; int ret = 0, len; DECLARE_WAITQUEUE(wait, current);
+ if (hidraw_is_revoked(list)) + return -ENODEV; + mutex_lock(&list->read_mutex);
while (ret == 0) { @@ -161,9 +169,13 @@ static ssize_t hidraw_send_report(struct file *file, const char __user *buffer,
static ssize_t hidraw_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos) { + struct hidraw_list *list = file->private_data; ssize_t ret; down_read(&minors_rwsem); - ret = hidraw_send_report(file, buffer, count, HID_OUTPUT_REPORT); + if (hidraw_is_revoked(list)) + ret = -ENODEV; + else + ret = hidraw_send_report(file, buffer, count, HID_OUTPUT_REPORT); up_read(&minors_rwsem); return ret; } @@ -256,7 +268,7 @@ static __poll_t hidraw_poll(struct file *file, poll_table *wait) poll_wait(file, &list->hidraw->wait, wait); if (list->head != list->tail) mask |= EPOLLIN | EPOLLRDNORM; - if (!list->hidraw->exist) + if (!list->hidraw->exist || hidraw_is_revoked(list)) mask |= EPOLLERR | EPOLLHUP; return mask; } @@ -320,6 +332,9 @@ static int hidraw_fasync(int fd, struct file *file, int on) { struct hidraw_list *list = file->private_data;
+ if (hidraw_is_revoked(list)) + return -ENODEV; + return fasync_helper(fd, file, on, &list->fasync); }
@@ -372,6 +387,13 @@ static int hidraw_release(struct inode * inode, struct file * file) return 0; }
+static int hidraw_revoke(struct hidraw_list *list) +{ + list->revoked = true; + + return 0; +} + static long hidraw_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { @@ -379,11 +401,12 @@ static long hidraw_ioctl(struct file *file, unsigned int cmd, unsigned int minor = iminor(inode); long ret = 0; struct hidraw *dev; + struct hidraw_list *list = file->private_data; void __user *user_arg = (void __user*) arg;
down_read(&minors_rwsem); dev = hidraw_table[minor]; - if (!dev || !dev->exist) { + if (!dev || !dev->exist || hidraw_is_revoked(list)) { ret = -ENODEV; goto out; } @@ -421,6 +444,14 @@ static long hidraw_ioctl(struct file *file, unsigned int cmd, ret = -EFAULT; break; } + case HIDIOCREVOKE: + { + if (user_arg) + ret = -EINVAL; + else + ret = hidraw_revoke(list); + break; + } default: { struct hid_device *hid = dev->hid; @@ -527,7 +558,7 @@ int hidraw_report_event(struct hid_device *hid, u8 *data, int len) list_for_each_entry(list, &dev->list, node) { int new_head = (list->head + 1) & (HIDRAW_BUFFER_SIZE - 1);
- if (new_head == list->tail) + if (hidraw_is_revoked(list) || new_head == list->tail) continue;
if (!(list->buffer[list->head].value = kmemdup(data, len, GFP_ATOMIC))) { diff --git a/include/linux/hidraw.h b/include/linux/hidraw.h index cd67f4ca5599..18fd30a288de 100644 --- a/include/linux/hidraw.h +++ b/include/linux/hidraw.h @@ -32,6 +32,7 @@ struct hidraw_list { struct hidraw *hidraw; struct list_head node; struct mutex read_mutex; + bool revoked; };
#ifdef CONFIG_HIDRAW diff --git a/include/uapi/linux/hidraw.h b/include/uapi/linux/hidraw.h index 33ebad81720a..d5ee269864e0 100644 --- a/include/uapi/linux/hidraw.h +++ b/include/uapi/linux/hidraw.h @@ -46,6 +46,7 @@ struct hidraw_devinfo { /* The first byte of SOUTPUT and GOUTPUT is the report number */ #define HIDIOCSOUTPUT(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x0B, len) #define HIDIOCGOUTPUT(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x0C, len) +#define HIDIOCREVOKE _IOW('H', 0x0D, int) /* Revoke device access */
#define HIDRAW_FIRST_MINOR 0 #define HIDRAW_MAX_DEVICES 64