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Diffstat (limited to 'drivers/hid/uhid.c')
-rw-r--r--drivers/hid/uhid.c83
1 files changed, 50 insertions, 33 deletions
diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 840634e0f1e3..21a70420151e 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -1,13 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
/*
* User-space I/O driver support for HID subsystem
* Copyright (c) 2012 David Herrmann
*/
/*
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the Free
- * Software Foundation; either version 2 of the License, or (at your option)
- * any later version.
*/
#include <linux/atomic.h>
@@ -31,11 +28,22 @@
struct uhid_device {
struct mutex devlock;
+
+ /* This flag tracks whether the HID device is usable for commands from
+ * userspace. The flag is already set before hid_add_device(), which
+ * runs in workqueue context, to allow hid_add_device() to communicate
+ * with userspace.
+ * However, if hid_add_device() fails, the flag is cleared without
+ * holding devlock.
+ * We guarantee that if @running changes from true to false while you're
+ * holding @devlock, it's still fine to access @hid.
+ */
bool running;
__u8 *rd_data;
uint rd_size;
+ /* When this is NULL, userspace may use UHID_CREATE/UHID_CREATE2. */
struct hid_device *hid;
struct uhid_event input_buf;
@@ -66,9 +74,18 @@ static void uhid_device_add_worker(struct work_struct *work)
if (ret) {
hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
- hid_destroy_device(uhid->hid);
- uhid->hid = NULL;
- uhid->running = false;
+ /* We used to call hid_destroy_device() here, but that's really
+ * messy to get right because we have to coordinate with
+ * concurrent writes from userspace that might be in the middle
+ * of using uhid->hid.
+ * Just leave uhid->hid as-is for now, and clean it up when
+ * userspace tries to close or reinitialize the uhid instance.
+ *
+ * However, we do have to clear the ->running flag and do a
+ * wakeup to make sure userspace knows that the device is gone.
+ */
+ WRITE_ONCE(uhid->running, false);
+ wake_up_interruptible(&uhid->report_wait);
}
}
@@ -177,9 +194,9 @@ static int __uhid_report_queue_and_wait(struct uhid_device *uhid,
spin_unlock_irqrestore(&uhid->qlock, flags);
ret = wait_event_interruptible_timeout(uhid->report_wait,
- !uhid->report_running || !uhid->running,
+ !uhid->report_running || !READ_ONCE(uhid->running),
5 * HZ);
- if (!ret || !uhid->running || uhid->report_running)
+ if (!ret || !READ_ONCE(uhid->running) || uhid->report_running)
ret = -EIO;
else if (ret < 0)
ret = -ERESTARTSYS;
@@ -220,7 +237,7 @@ static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
struct uhid_event *ev;
int ret;
- if (!uhid->running)
+ if (!READ_ONCE(uhid->running))
return -EIO;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
@@ -262,7 +279,7 @@ static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
struct uhid_event *ev;
int ret;
- if (!uhid->running || count > UHID_DATA_MAX)
+ if (!READ_ONCE(uhid->running) || count > UHID_DATA_MAX)
return -EIO;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
@@ -370,7 +387,7 @@ static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
}
-struct hid_ll_driver uhid_hid_driver = {
+static const struct hid_ll_driver uhid_hid_driver = {
.start = uhid_hid_start,
.stop = uhid_hid_stop,
.open = uhid_hid_open,
@@ -378,8 +395,8 @@ struct hid_ll_driver uhid_hid_driver = {
.parse = uhid_hid_parse,
.raw_request = uhid_hid_raw_request,
.output_report = uhid_hid_output_report,
+ .max_buffer_size = UHID_DATA_MAX,
};
-EXPORT_SYMBOL_GPL(uhid_hid_driver);
#ifdef CONFIG_COMPAT
@@ -473,11 +490,11 @@ static int uhid_dev_create2(struct uhid_device *uhid,
const struct uhid_event *ev)
{
struct hid_device *hid;
- size_t rd_size, len;
+ size_t rd_size;
void *rd_data;
int ret;
- if (uhid->running)
+ if (uhid->hid)
return -EALREADY;
rd_size = ev->u.create2.rd_size;
@@ -497,13 +514,12 @@ static int uhid_dev_create2(struct uhid_device *uhid,
goto err_free;
}
- /* @hid is zero-initialized, strncpy() is correct, strlcpy() not */
- len = min(sizeof(hid->name), sizeof(ev->u.create2.name)) - 1;
- strncpy(hid->name, ev->u.create2.name, len);
- len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys)) - 1;
- strncpy(hid->phys, ev->u.create2.phys, len);
- len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq)) - 1;
- strncpy(hid->uniq, ev->u.create2.uniq, len);
+ BUILD_BUG_ON(sizeof(hid->name) != sizeof(ev->u.create2.name));
+ strscpy(hid->name, ev->u.create2.name, sizeof(hid->name));
+ BUILD_BUG_ON(sizeof(hid->phys) != sizeof(ev->u.create2.phys));
+ strscpy(hid->phys, ev->u.create2.phys, sizeof(hid->phys));
+ BUILD_BUG_ON(sizeof(hid->uniq) != sizeof(ev->u.create2.uniq));
+ strscpy(hid->uniq, ev->u.create2.uniq, sizeof(hid->uniq));
hid->ll_driver = &uhid_hid_driver;
hid->bus = ev->u.create2.bus;
@@ -559,15 +575,16 @@ static int uhid_dev_create(struct uhid_device *uhid,
static int uhid_dev_destroy(struct uhid_device *uhid)
{
- if (!uhid->running)
+ if (!uhid->hid)
return -EINVAL;
- uhid->running = false;
+ WRITE_ONCE(uhid->running, false);
wake_up_interruptible(&uhid->report_wait);
cancel_work_sync(&uhid->worker);
hid_destroy_device(uhid->hid);
+ uhid->hid = NULL;
kfree(uhid->rd_data);
return 0;
@@ -575,7 +592,7 @@ static int uhid_dev_destroy(struct uhid_device *uhid)
static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
{
- if (!uhid->running)
+ if (!READ_ONCE(uhid->running))
return -EINVAL;
hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
@@ -586,7 +603,7 @@ static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
{
- if (!uhid->running)
+ if (!READ_ONCE(uhid->running))
return -EINVAL;
hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input2.data,
@@ -598,7 +615,7 @@ static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
static int uhid_dev_get_report_reply(struct uhid_device *uhid,
struct uhid_event *ev)
{
- if (!uhid->running)
+ if (!READ_ONCE(uhid->running))
return -EINVAL;
uhid_report_wake_up(uhid, ev->u.get_report_reply.id, ev);
@@ -608,7 +625,7 @@ static int uhid_dev_get_report_reply(struct uhid_device *uhid,
static int uhid_dev_set_report_reply(struct uhid_device *uhid,
struct uhid_event *ev)
{
- if (!uhid->running)
+ if (!READ_ONCE(uhid->running))
return -EINVAL;
uhid_report_wake_up(uhid, ev->u.set_report_reply.id, ev);
@@ -632,7 +649,7 @@ static int uhid_char_open(struct inode *inode, struct file *file)
INIT_WORK(&uhid->worker, uhid_device_add_worker);
file->private_data = uhid;
- nonseekable_open(inode, file);
+ stream_open(inode, file);
return 0;
}
@@ -729,7 +746,7 @@ static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
* copied from, so it's unsafe to allow this with elevated
* privileges (e.g. from a setuid binary) or via kernel_write().
*/
- if (file->f_cred != current_cred() || uaccess_kernel()) {
+ if (file->f_cred != current_cred()) {
pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n",
task_tgid_vnr(current), current->comm);
ret = -EACCES;
@@ -769,13 +786,14 @@ unlock:
static __poll_t uhid_char_poll(struct file *file, poll_table *wait)
{
struct uhid_device *uhid = file->private_data;
+ __poll_t mask = EPOLLOUT | EPOLLWRNORM; /* uhid is always writable */
poll_wait(file, &uhid->waitq, wait);
if (uhid->head != uhid->tail)
- return EPOLLIN | EPOLLRDNORM;
+ mask |= EPOLLIN | EPOLLRDNORM;
- return 0;
+ return mask;
}
static const struct file_operations uhid_fops = {
@@ -785,7 +803,6 @@ static const struct file_operations uhid_fops = {
.read = uhid_char_read,
.write = uhid_char_write,
.poll = uhid_char_poll,
- .llseek = no_llseek,
};
static struct miscdevice uhid_misc = {
generated by cgit (git 2.34.1) at 2025-12-24 22:04:26 +0000