projects/linux·blob v5.9-rc7 · refs

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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/timerfd.c
4 *
5 * Copyright (C) 2007 Davide Libenzi <[email protected]>
6 *
7 *
8 * Thanks to Thomas Gleixner for code reviews and useful comments.
9 *
10 */
11
12#include <linux/alarmtimer.h>
13#include <linux/file.h>
14#include <linux/poll.h>
15#include <linux/init.h>
16#include <linux/fs.h>
17#include <linux/sched.h>
18#include <linux/kernel.h>
19#include <linux/slab.h>
20#include <linux/list.h>
21#include <linux/spinlock.h>
22#include <linux/time.h>
23#include <linux/hrtimer.h>
24#include <linux/anon_inodes.h>
25#include <linux/timerfd.h>
26#include <linux/syscalls.h>
27#include <linux/compat.h>
28#include <linux/rcupdate.h>
29#include <linux/time_namespace.h>
30
31struct timerfd_ctx {
32 union {
33 struct hrtimer tmr;
34 struct alarm alarm;
35 } t;
36 ktime_t tintv;
37 ktime_t moffs;
38 wait_queue_head_t wqh;
39 u64 ticks;
40 int clockid;
41 short unsigned expired;
42 short unsigned settime_flags; /* to show in fdinfo */
43 struct rcu_head rcu;
44 struct list_head clist;
45 spinlock_t cancel_lock;
46 bool might_cancel;
47};
48
49static LIST_HEAD(cancel_list);
50static DEFINE_SPINLOCK(cancel_lock);
51
52static inline bool isalarm(struct timerfd_ctx *ctx)
53{
54 return ctx->clockid == CLOCK_REALTIME_ALARM ||
55 ctx->clockid == CLOCK_BOOTTIME_ALARM;
56}
57
58/*
59 * This gets called when the timer event triggers. We set the "expired"
60 * flag, but we do not re-arm the timer (in case it's necessary,
61 * tintv != 0) until the timer is accessed.
62 */
63static void timerfd_triggered(struct timerfd_ctx *ctx)
64{
65 unsigned long flags;
66
67 spin_lock_irqsave(&ctx->wqh.lock, flags);
68 ctx->expired = 1;
69 ctx->ticks++;
70 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
71 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
72}
73
74static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
75{
76 struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx,
77 t.tmr);
78 timerfd_triggered(ctx);
79 return HRTIMER_NORESTART;
80}
81
82static enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,
83 ktime_t now)
84{
85 struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,
86 t.alarm);
87 timerfd_triggered(ctx);
88 return ALARMTIMER_NORESTART;
89}
90
91/*
92 * Called when the clock was set to cancel the timers in the cancel
93 * list. This will wake up processes waiting on these timers. The
94 * wake-up requires ctx->ticks to be non zero, therefore we increment
95 * it before calling wake_up_locked().
96 */
97void timerfd_clock_was_set(void)
98{
99 ktime_t moffs = ktime_mono_to_real(0);
100 struct timerfd_ctx *ctx;
101 unsigned long flags;
102
103 rcu_read_lock();
104 list_for_each_entry_rcu(ctx, &cancel_list, clist) {
105 if (!ctx->might_cancel)
106 continue;
107 spin_lock_irqsave(&ctx->wqh.lock, flags);
108 if (ctx->moffs != moffs) {
109 ctx->moffs = KTIME_MAX;
110 ctx->ticks++;
111 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
112 }
113 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
114 }
115 rcu_read_unlock();
116}
117
118static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)
119{
120 if (ctx->might_cancel) {
121 ctx->might_cancel = false;
122 spin_lock(&cancel_lock);
123 list_del_rcu(&ctx->clist);
124 spin_unlock(&cancel_lock);
125 }
126}
127
128static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
129{
130 spin_lock(&ctx->cancel_lock);
131 __timerfd_remove_cancel(ctx);
132 spin_unlock(&ctx->cancel_lock);
133}
134
135static bool timerfd_canceled(struct timerfd_ctx *ctx)
136{
137 if (!ctx->might_cancel || ctx->moffs != KTIME_MAX)
138 return false;
139 ctx->moffs = ktime_mono_to_real(0);
140 return true;
141}
142
143static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
144{
145 spin_lock(&ctx->cancel_lock);
146 if ((ctx->clockid == CLOCK_REALTIME ||
147 ctx->clockid == CLOCK_REALTIME_ALARM) &&
148 (flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) {
149 if (!ctx->might_cancel) {
150 ctx->might_cancel = true;
151 spin_lock(&cancel_lock);
152 list_add_rcu(&ctx->clist, &cancel_list);
153 spin_unlock(&cancel_lock);
154 }
155 } else {
156 __timerfd_remove_cancel(ctx);
157 }
158 spin_unlock(&ctx->cancel_lock);
159}
160
161static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
162{
163 ktime_t remaining;
164
165 if (isalarm(ctx))
166 remaining = alarm_expires_remaining(&ctx->t.alarm);
167 else
168 remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);
169
170 return remaining < 0 ? 0: remaining;
171}
172
173static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
174 const struct itimerspec64 *ktmr)
175{
176 enum hrtimer_mode htmode;
177 ktime_t texp;
178 int clockid = ctx->clockid;
179
180 htmode = (flags & TFD_TIMER_ABSTIME) ?
181 HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
182
183 texp = timespec64_to_ktime(ktmr->it_value);
184 ctx->expired = 0;
185 ctx->ticks = 0;
186 ctx->tintv = timespec64_to_ktime(ktmr->it_interval);
187
188 if (isalarm(ctx)) {
189 alarm_init(&ctx->t.alarm,
190 ctx->clockid == CLOCK_REALTIME_ALARM ?
191 ALARM_REALTIME : ALARM_BOOTTIME,
192 timerfd_alarmproc);
193 } else {
194 hrtimer_init(&ctx->t.tmr, clockid, htmode);
195 hrtimer_set_expires(&ctx->t.tmr, texp);
196 ctx->t.tmr.function = timerfd_tmrproc;
197 }
198
199 if (texp != 0) {
200 if (flags & TFD_TIMER_ABSTIME)
201 texp = timens_ktime_to_host(clockid, texp);
202 if (isalarm(ctx)) {
203 if (flags & TFD_TIMER_ABSTIME)
204 alarm_start(&ctx->t.alarm, texp);
205 else
206 alarm_start_relative(&ctx->t.alarm, texp);
207 } else {
208 hrtimer_start(&ctx->t.tmr, texp, htmode);
209 }
210
211 if (timerfd_canceled(ctx))
212 return -ECANCELED;
213 }
214
215 ctx->settime_flags = flags & TFD_SETTIME_FLAGS;
216 return 0;
217}
218
219static int timerfd_release(struct inode *inode, struct file *file)
220{
221 struct timerfd_ctx *ctx = file->private_data;
222
223 timerfd_remove_cancel(ctx);
224
225 if (isalarm(ctx))
226 alarm_cancel(&ctx->t.alarm);
227 else
228 hrtimer_cancel(&ctx->t.tmr);
229 kfree_rcu(ctx, rcu);
230 return 0;
231}
232
233static __poll_t timerfd_poll(struct file *file, poll_table *wait)
234{
235 struct timerfd_ctx *ctx = file->private_data;
236 __poll_t events = 0;
237 unsigned long flags;
238
239 poll_wait(file, &ctx->wqh, wait);
240
241 spin_lock_irqsave(&ctx->wqh.lock, flags);
242 if (ctx->ticks)
243 events |= EPOLLIN;
244 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
245
246 return events;
247}
248
249static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
250 loff_t *ppos)
251{
252 struct timerfd_ctx *ctx = file->private_data;
253 ssize_t res;
254 u64 ticks = 0;
255
256 if (count < sizeof(ticks))
257 return -EINVAL;
258 spin_lock_irq(&ctx->wqh.lock);
259 if (file->f_flags & O_NONBLOCK)
260 res = -EAGAIN;
261 else
262 res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
263
264 /*
265 * If clock has changed, we do not care about the
266 * ticks and we do not rearm the timer. Userspace must
267 * reevaluate anyway.
268 */
269 if (timerfd_canceled(ctx)) {
270 ctx->ticks = 0;
271 ctx->expired = 0;
272 res = -ECANCELED;
273 }
274
275 if (ctx->ticks) {
276 ticks = ctx->ticks;
277
278 if (ctx->expired && ctx->tintv) {
279 /*
280 * If tintv != 0, this is a periodic timer that
281 * needs to be re-armed. We avoid doing it in the timer
282 * callback to avoid DoS attacks specifying a very
283 * short timer period.
284 */
285 if (isalarm(ctx)) {
286 ticks += alarm_forward_now(
287 &ctx->t.alarm, ctx->tintv) - 1;
288 alarm_restart(&ctx->t.alarm);
289 } else {
290 ticks += hrtimer_forward_now(&ctx->t.tmr,
291 ctx->tintv) - 1;
292 hrtimer_restart(&ctx->t.tmr);
293 }
294 }
295 ctx->expired = 0;
296 ctx->ticks = 0;
297 }
298 spin_unlock_irq(&ctx->wqh.lock);
299 if (ticks)
300 res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
301 return res;
302}
303
304#ifdef CONFIG_PROC_FS
305static void timerfd_show(struct seq_file *m, struct file *file)
306{
307 struct timerfd_ctx *ctx = file->private_data;
308 struct timespec64 value, interval;
309
310 spin_lock_irq(&ctx->wqh.lock);
311 value = ktime_to_timespec64(timerfd_get_remaining(ctx));
312 interval = ktime_to_timespec64(ctx->tintv);
313 spin_unlock_irq(&ctx->wqh.lock);
314
315 seq_printf(m,
316 "clockid: %d\n"
317 "ticks: %llu\n"
318 "settime flags: 0%o\n"
319 "it_value: (%llu, %llu)\n"
320 "it_interval: (%llu, %llu)\n",
321 ctx->clockid,
322 (unsigned long long)ctx->ticks,
323 ctx->settime_flags,
324 (unsigned long long)value.tv_sec,
325 (unsigned long long)value.tv_nsec,
326 (unsigned long long)interval.tv_sec,
327 (unsigned long long)interval.tv_nsec);
328}
329#else
330#define timerfd_show NULL
331#endif
332
333#ifdef CONFIG_CHECKPOINT_RESTORE
334static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
335{
336 struct timerfd_ctx *ctx = file->private_data;
337 int ret = 0;
338
339 switch (cmd) {
340 case TFD_IOC_SET_TICKS: {
341 u64 ticks;
342
343 if (copy_from_user(&ticks, (u64 __user *)arg, sizeof(ticks)))
344 return -EFAULT;
345 if (!ticks)
346 return -EINVAL;
347
348 spin_lock_irq(&ctx->wqh.lock);
349 if (!timerfd_canceled(ctx)) {
350 ctx->ticks = ticks;
351 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
352 } else
353 ret = -ECANCELED;
354 spin_unlock_irq(&ctx->wqh.lock);
355 break;
356 }
357 default:
358 ret = -ENOTTY;
359 break;
360 }
361
362 return ret;
363}
364#else
365#define timerfd_ioctl NULL
366#endif
367
368static const struct file_operations timerfd_fops = {
369 .release = timerfd_release,
370 .poll = timerfd_poll,
371 .read = timerfd_read,
372 .llseek = noop_llseek,
373 .show_fdinfo = timerfd_show,
374 .unlocked_ioctl = timerfd_ioctl,
375};
376
377static int timerfd_fget(int fd, struct fd *p)
378{
379 struct fd f = fdget(fd);
380 if (!f.file)
381 return -EBADF;
382 if (f.file->f_op != &timerfd_fops) {
383 fdput(f);
384 return -EINVAL;
385 }
386 *p = f;
387 return 0;
388}
389
390SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
391{
392 int ufd;
393 struct timerfd_ctx *ctx;
394
395 /* Check the TFD_* constants for consistency. */
396 BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
397 BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
398
399 if ((flags & ~TFD_CREATE_FLAGS) ||
400 (clockid != CLOCK_MONOTONIC &&
401 clockid != CLOCK_REALTIME &&
402 clockid != CLOCK_REALTIME_ALARM &&
403 clockid != CLOCK_BOOTTIME &&
404 clockid != CLOCK_BOOTTIME_ALARM))
405 return -EINVAL;
406
407 if ((clockid == CLOCK_REALTIME_ALARM ||
408 clockid == CLOCK_BOOTTIME_ALARM) &&
409 !capable(CAP_WAKE_ALARM))
410 return -EPERM;
411
412 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
413 if (!ctx)
414 return -ENOMEM;
415
416 init_waitqueue_head(&ctx->wqh);
417 spin_lock_init(&ctx->cancel_lock);
418 ctx->clockid = clockid;
419
420 if (isalarm(ctx))
421 alarm_init(&ctx->t.alarm,
422 ctx->clockid == CLOCK_REALTIME_ALARM ?
423 ALARM_REALTIME : ALARM_BOOTTIME,
424 timerfd_alarmproc);
425 else
426 hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);
427
428 ctx->moffs = ktime_mono_to_real(0);
429
430 ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
431 O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
432 if (ufd < 0)
433 kfree(ctx);
434
435 return ufd;
436}
437
438static int do_timerfd_settime(int ufd, int flags,
439 const struct itimerspec64 *new,
440 struct itimerspec64 *old)
441{
442 struct fd f;
443 struct timerfd_ctx *ctx;
444 int ret;
445
446 if ((flags & ~TFD_SETTIME_FLAGS) ||
447 !itimerspec64_valid(new))
448 return -EINVAL;
449
450 ret = timerfd_fget(ufd, &f);
451 if (ret)
452 return ret;
453 ctx = f.file->private_data;
454
455 if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) {
456 fdput(f);
457 return -EPERM;
458 }
459
460 timerfd_setup_cancel(ctx, flags);
461
462 /*
463 * We need to stop the existing timer before reprogramming
464 * it to the new values.
465 */
466 for (;;) {
467 spin_lock_irq(&ctx->wqh.lock);
468
469 if (isalarm(ctx)) {
470 if (alarm_try_to_cancel(&ctx->t.alarm) >= 0)
471 break;
472 } else {
473 if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0)
474 break;
475 }
476 spin_unlock_irq(&ctx->wqh.lock);
477
478 if (isalarm(ctx))
479 hrtimer_cancel_wait_running(&ctx->t.alarm.timer);
480 else
481 hrtimer_cancel_wait_running(&ctx->t.tmr);
482 }
483
484 /*
485 * If the timer is expired and it's periodic, we need to advance it
486 * because the caller may want to know the previous expiration time.
487 * We do not update "ticks" and "expired" since the timer will be
488 * re-programmed again in the following timerfd_setup() call.
489 */
490 if (ctx->expired && ctx->tintv) {
491 if (isalarm(ctx))
492 alarm_forward_now(&ctx->t.alarm, ctx->tintv);
493 else
494 hrtimer_forward_now(&ctx->t.tmr, ctx->tintv);
495 }
496
497 old->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
498 old->it_interval = ktime_to_timespec64(ctx->tintv);
499
500 /*
501 * Re-program the timer to the new value ...
502 */
503 ret = timerfd_setup(ctx, flags, new);
504
505 spin_unlock_irq(&ctx->wqh.lock);
506 fdput(f);
507 return ret;
508}
509
510static int do_timerfd_gettime(int ufd, struct itimerspec64 *t)
511{
512 struct fd f;
513 struct timerfd_ctx *ctx;
514 int ret = timerfd_fget(ufd, &f);
515 if (ret)
516 return ret;
517 ctx = f.file->private_data;
518
519 spin_lock_irq(&ctx->wqh.lock);
520 if (ctx->expired && ctx->tintv) {
521 ctx->expired = 0;
522
523 if (isalarm(ctx)) {
524 ctx->ticks +=
525 alarm_forward_now(
526 &ctx->t.alarm, ctx->tintv) - 1;
527 alarm_restart(&ctx->t.alarm);
528 } else {
529 ctx->ticks +=
530 hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)
531 - 1;
532 hrtimer_restart(&ctx->t.tmr);
533 }
534 }
535 t->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
536 t->it_interval = ktime_to_timespec64(ctx->tintv);
537 spin_unlock_irq(&ctx->wqh.lock);
538 fdput(f);
539 return 0;
540}
541
542SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
543 const struct __kernel_itimerspec __user *, utmr,
544 struct __kernel_itimerspec __user *, otmr)
545{
546 struct itimerspec64 new, old;
547 int ret;
548
549 if (get_itimerspec64(&new, utmr))
550 return -EFAULT;
551 ret = do_timerfd_settime(ufd, flags, &new, &old);
552 if (ret)
553 return ret;
554 if (otmr && put_itimerspec64(&old, otmr))
555 return -EFAULT;
556
557 return ret;
558}
559
560SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct __kernel_itimerspec __user *, otmr)
561{
562 struct itimerspec64 kotmr;
563 int ret = do_timerfd_gettime(ufd, &kotmr);
564 if (ret)
565 return ret;
566 return put_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
567}
568
569#ifdef CONFIG_COMPAT_32BIT_TIME
570SYSCALL_DEFINE4(timerfd_settime32, int, ufd, int, flags,
571 const struct old_itimerspec32 __user *, utmr,
572 struct old_itimerspec32 __user *, otmr)
573{
574 struct itimerspec64 new, old;
575 int ret;
576
577 if (get_old_itimerspec32(&new, utmr))
578 return -EFAULT;
579 ret = do_timerfd_settime(ufd, flags, &new, &old);
580 if (ret)
581 return ret;
582 if (otmr && put_old_itimerspec32(&old, otmr))
583 return -EFAULT;
584 return ret;
585}
586
587SYSCALL_DEFINE2(timerfd_gettime32, int, ufd,
588 struct old_itimerspec32 __user *, otmr)
589{
590 struct itimerspec64 kotmr;
591 int ret = do_timerfd_gettime(ufd, &kotmr);
592 if (ret)
593 return ret;
594 return put_old_itimerspec32(&kotmr, otmr) ? -EFAULT : 0;
595}
596#endif