From 66d2a5952eab875f1286e04f738ef029afdaf013 Mon Sep 17 00:00:00 2001 From: Dmitry Torokhov Date: Tue, 1 Dec 2009 21:54:35 -0800 Subject: [PATCH] Input: keyboard - fix lack of locking when traversing handler->h_list Keyboard handler should not attempt to traverse handler->h_list on its own, without any locking, otherwise it races with registering and unregistering of input handles which leads to crashes. Introduce input_handler_for_each_handle() helper that allows safely iterate over all handles attached to a particular handler and switch keyboard handler to use it. Reported-by: Jim Paradis Signed-off-by: Dmitry Torokhov --- drivers/char/keyboard.c | 202 +++++++++++++++++++++------------------- drivers/input/input.c | 37 +++++++- include/linux/input.h | 10 +- 3 files changed, 148 insertions(+), 101 deletions(-) diff --git a/drivers/char/keyboard.c b/drivers/char/keyboard.c index ca090e57e16..ff8e9345f3c 100644 --- a/drivers/char/keyboard.c +++ b/drivers/char/keyboard.c @@ -46,8 +46,6 @@ extern void ctrl_alt_del(void); -#define to_handle_h(n) container_of(n, struct input_handle, h_node) - /* * Exported functions/variables */ @@ -191,78 +189,85 @@ EXPORT_SYMBOL_GPL(unregister_keyboard_notifier); * etc.). So this means that scancodes for the extra function keys won't * be valid for the first event device, but will be for the second. */ + +struct getset_keycode_data { + unsigned int scancode; + unsigned int keycode; + int error; +}; + +static int getkeycode_helper(struct input_handle *handle, void *data) +{ + struct getset_keycode_data *d = data; + + d->error = input_get_keycode(handle->dev, d->scancode, &d->keycode); + + return d->error == 0; /* stop as soon as we successfully get one */ +} + int getkeycode(unsigned int scancode) { - struct input_handle *handle; - int keycode; - int error = -ENODEV; + struct getset_keycode_data d = { scancode, 0, -ENODEV }; - list_for_each_entry(handle, &kbd_handler.h_list, h_node) { - error = input_get_keycode(handle->dev, scancode, &keycode); - if (!error) - return keycode; - } + input_handler_for_each_handle(&kbd_handler, &d, getkeycode_helper); - return error; + return d.error ?: d.keycode; +} + +static int setkeycode_helper(struct input_handle *handle, void *data) +{ + struct getset_keycode_data *d = data; + + d->error = input_set_keycode(handle->dev, d->scancode, d->keycode); + + return d->error == 0; /* stop as soon as we successfully set one */ } int setkeycode(unsigned int scancode, unsigned int keycode) { - struct input_handle *handle; - int error = -ENODEV; + struct getset_keycode_data d = { scancode, keycode, -ENODEV }; - list_for_each_entry(handle, &kbd_handler.h_list, h_node) { - error = input_set_keycode(handle->dev, scancode, keycode); - if (!error) - break; - } + input_handler_for_each_handle(&kbd_handler, &d, setkeycode_helper); - return error; + return d.error; } /* * Making beeps and bells. */ -static void kd_nosound(unsigned long ignored) + +static int kd_sound_helper(struct input_handle *handle, void *data) { - struct input_handle *handle; + unsigned int *hz = data; + struct input_dev *dev = handle->dev; - list_for_each_entry(handle, &kbd_handler.h_list, h_node) { - if (test_bit(EV_SND, handle->dev->evbit)) { - if (test_bit(SND_TONE, handle->dev->sndbit)) - input_inject_event(handle, EV_SND, SND_TONE, 0); - if (test_bit(SND_BELL, handle->dev->sndbit)) - input_inject_event(handle, EV_SND, SND_BELL, 0); - } + if (test_bit(EV_SND, dev->evbit)) { + if (test_bit(SND_TONE, dev->sndbit)) + input_inject_event(handle, EV_SND, SND_TONE, *hz); + if (test_bit(SND_BELL, handle->dev->sndbit)) + input_inject_event(handle, EV_SND, SND_BELL, *hz ? 1 : 0); } + + return 0; +} + +static void kd_nosound(unsigned long ignored) +{ + static unsigned int zero; + + input_handler_for_each_handle(&kbd_handler, &zero, kd_sound_helper); } static DEFINE_TIMER(kd_mksound_timer, kd_nosound, 0, 0); void kd_mksound(unsigned int hz, unsigned int ticks) { - struct list_head *node; + del_timer_sync(&kd_mksound_timer); - del_timer(&kd_mksound_timer); + input_handler_for_each_handle(&kbd_handler, &hz, kd_sound_helper); - if (hz) { - list_for_each_prev(node, &kbd_handler.h_list) { - struct input_handle *handle = to_handle_h(node); - if (test_bit(EV_SND, handle->dev->evbit)) { - if (test_bit(SND_TONE, handle->dev->sndbit)) { - input_inject_event(handle, EV_SND, SND_TONE, hz); - break; - } - if (test_bit(SND_BELL, handle->dev->sndbit)) { - input_inject_event(handle, EV_SND, SND_BELL, 1); - break; - } - } - } - if (ticks) - mod_timer(&kd_mksound_timer, jiffies + ticks); - } else - kd_nosound(0); + if (hz && ticks) + mod_timer(&kd_mksound_timer, jiffies + ticks); } EXPORT_SYMBOL(kd_mksound); @@ -270,27 +275,34 @@ EXPORT_SYMBOL(kd_mksound); * Setting the keyboard rate. */ -int kbd_rate(struct kbd_repeat *rep) +static int kbd_rate_helper(struct input_handle *handle, void *data) { - struct list_head *node; - unsigned int d = 0; - unsigned int p = 0; - - list_for_each(node, &kbd_handler.h_list) { - struct input_handle *handle = to_handle_h(node); - struct input_dev *dev = handle->dev; - - if (test_bit(EV_REP, dev->evbit)) { - if (rep->delay > 0) - input_inject_event(handle, EV_REP, REP_DELAY, rep->delay); - if (rep->period > 0) - input_inject_event(handle, EV_REP, REP_PERIOD, rep->period); - d = dev->rep[REP_DELAY]; - p = dev->rep[REP_PERIOD]; - } + struct input_dev *dev = handle->dev; + struct kbd_repeat *rep = data; + + if (test_bit(EV_REP, dev->evbit)) { + + if (rep[0].delay > 0) + input_inject_event(handle, + EV_REP, REP_DELAY, rep[0].delay); + if (rep[0].period > 0) + input_inject_event(handle, + EV_REP, REP_PERIOD, rep[0].period); + + rep[1].delay = dev->rep[REP_DELAY]; + rep[1].period = dev->rep[REP_PERIOD]; } - rep->delay = d; - rep->period = p; + + return 0; +} + +int kbd_rate(struct kbd_repeat *rep) +{ + struct kbd_repeat data[2] = { *rep }; + + input_handler_for_each_handle(&kbd_handler, data, kbd_rate_helper); + *rep = data[1]; /* Copy currently used settings */ + return 0; } @@ -998,36 +1010,36 @@ static inline unsigned char getleds(void) return leds; } +static int kbd_update_leds_helper(struct input_handle *handle, void *data) +{ + unsigned char leds = *(unsigned char *)data; + + if (test_bit(EV_LED, handle->dev->evbit)) { + input_inject_event(handle, EV_LED, LED_SCROLLL, !!(leds & 0x01)); + input_inject_event(handle, EV_LED, LED_NUML, !!(leds & 0x02)); + input_inject_event(handle, EV_LED, LED_CAPSL, !!(leds & 0x04)); + input_inject_event(handle, EV_SYN, SYN_REPORT, 0); + } + + return 0; +} + /* - * This routine is the bottom half of the keyboard interrupt - * routine, and runs with all interrupts enabled. It does - * console changing, led setting and copy_to_cooked, which can - * take a reasonably long time. - * - * Aside from timing (which isn't really that important for - * keyboard interrupts as they happen often), using the software - * interrupt routines for this thing allows us to easily mask - * this when we don't want any of the above to happen. - * This allows for easy and efficient race-condition prevention - * for kbd_start => input_inject_event(dev, EV_LED, ...) => ... + * This is the tasklet that updates LED state on all keyboards + * attached to the box. The reason we use tasklet is that we + * need to handle the scenario when keyboard handler is not + * registered yet but we already getting updates form VT to + * update led state. */ - static void kbd_bh(unsigned long dummy) { - struct list_head *node; unsigned char leds = getleds(); if (leds != ledstate) { - list_for_each(node, &kbd_handler.h_list) { - struct input_handle *handle = to_handle_h(node); - input_inject_event(handle, EV_LED, LED_SCROLLL, !!(leds & 0x01)); - input_inject_event(handle, EV_LED, LED_NUML, !!(leds & 0x02)); - input_inject_event(handle, EV_LED, LED_CAPSL, !!(leds & 0x04)); - input_inject_event(handle, EV_SYN, SYN_REPORT, 0); - } + input_handler_for_each_handle(&kbd_handler, &leds, + kbd_update_leds_helper); + ledstate = leds; } - - ledstate = leds; } DECLARE_TASKLET_DISABLED(keyboard_tasklet, kbd_bh, 0); @@ -1370,15 +1382,11 @@ static void kbd_disconnect(struct input_handle *handle) */ static void kbd_start(struct input_handle *handle) { - unsigned char leds = ledstate; - tasklet_disable(&keyboard_tasklet); - if (leds != 0xff) { - input_inject_event(handle, EV_LED, LED_SCROLLL, !!(leds & 0x01)); - input_inject_event(handle, EV_LED, LED_NUML, !!(leds & 0x02)); - input_inject_event(handle, EV_LED, LED_CAPSL, !!(leds & 0x04)); - input_inject_event(handle, EV_SYN, SYN_REPORT, 0); - } + + if (ledstate != 0xff) + kbd_update_leds_helper(handle, &ledstate); + tasklet_enable(&keyboard_tasklet); } diff --git a/drivers/input/input.c b/drivers/input/input.c index cc763c96fad..5d6421bde4b 100644 --- a/drivers/input/input.c +++ b/drivers/input/input.c @@ -1650,6 +1650,38 @@ void input_unregister_handler(struct input_handler *handler) } EXPORT_SYMBOL(input_unregister_handler); +/** + * input_handler_for_each_handle - handle iterator + * @handler: input handler to iterate + * @data: data for the callback + * @fn: function to be called for each handle + * + * Iterate over @bus's list of devices, and call @fn for each, passing + * it @data and stop when @fn returns a non-zero value. The function is + * using RCU to traverse the list and therefore may be usind in atonic + * contexts. The @fn callback is invoked from RCU critical section and + * thus must not sleep. + */ +int input_handler_for_each_handle(struct input_handler *handler, void *data, + int (*fn)(struct input_handle *, void *)) +{ + struct input_handle *handle; + int retval = 0; + + rcu_read_lock(); + + list_for_each_entry_rcu(handle, &handler->h_list, h_node) { + retval = fn(handle, data); + if (retval) + break; + } + + rcu_read_unlock(); + + return retval; +} +EXPORT_SYMBOL(input_handler_for_each_handle); + /** * input_register_handle - register a new input handle * @handle: handle to register @@ -1683,7 +1715,7 @@ int input_register_handle(struct input_handle *handle) * we can't be racing with input_unregister_handle() * and so separate lock is not needed here. */ - list_add_tail(&handle->h_node, &handler->h_list); + list_add_tail_rcu(&handle->h_node, &handler->h_list); if (handler->start) handler->start(handle); @@ -1706,7 +1738,7 @@ void input_unregister_handle(struct input_handle *handle) { struct input_dev *dev = handle->dev; - list_del_init(&handle->h_node); + list_del_rcu(&handle->h_node); /* * Take dev->mutex to prevent race with input_release_device(). @@ -1714,6 +1746,7 @@ void input_unregister_handle(struct input_handle *handle) mutex_lock(&dev->mutex); list_del_rcu(&handle->d_node); mutex_unlock(&dev->mutex); + synchronize_rcu(); } EXPORT_SYMBOL(input_unregister_handle); diff --git a/include/linux/input.h b/include/linux/input.h index 56d8e048c64..db563bbac9d 100644 --- a/include/linux/input.h +++ b/include/linux/input.h @@ -1021,9 +1021,12 @@ struct ff_effect { * @keycodesize: size of elements in keycode table * @keycode: map of scancodes to keycodes for this device * @setkeycode: optional method to alter current keymap, used to implement - * sparse keymaps. If not supplied default mechanism will be used + * sparse keymaps. If not supplied default mechanism will be used. + * The method is being called while holding event_lock and thus must + * not sleep * @getkeycode: optional method to retrieve current keymap. If not supplied - * default mechanism will be used + * default mechanism will be used. The method is being called while + * holding event_lock and thus must not sleep * @ff: force feedback structure associated with the device if device * supports force feedback effects * @repeat_key: stores key code of the last key pressed; used to implement @@ -1295,6 +1298,9 @@ void input_unregister_device(struct input_dev *); int __must_check input_register_handler(struct input_handler *); void input_unregister_handler(struct input_handler *); +int input_handler_for_each_handle(struct input_handler *, void *data, + int (*fn)(struct input_handle *, void *)); + int input_register_handle(struct input_handle *); void input_unregister_handle(struct input_handle *); -- 2.41.0