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![Davide Libenzi](/assets/img/avatar_default.png)
As requested by Michael, add a missing check for valid flags in timerfd_settime(), and make it return EINVAL in case some extra bits are set. Michael said: If this is to be any use to userland apps that want to check flag support (perhaps it is too late already), then the sooner we get it into the kernel the better: 2.6.29 would be good; earlier stables as well would be even better. [akpm@linux-foundation.org: remove unused TFD_FLAGS_SET] Acked-by: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Cc: <stable@kernel.org> [2.6.27.x, 2.6.28.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
293 lines
6.8 KiB
C
293 lines
6.8 KiB
C
/*
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* fs/timerfd.c
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*
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* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
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*
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*
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* Thanks to Thomas Gleixner for code reviews and useful comments.
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*
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*/
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#include <linux/file.h>
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#include <linux/poll.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/spinlock.h>
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#include <linux/time.h>
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#include <linux/hrtimer.h>
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#include <linux/anon_inodes.h>
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#include <linux/timerfd.h>
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#include <linux/syscalls.h>
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struct timerfd_ctx {
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struct hrtimer tmr;
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ktime_t tintv;
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wait_queue_head_t wqh;
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u64 ticks;
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int expired;
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int clockid;
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};
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/*
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* This gets called when the timer event triggers. We set the "expired"
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* flag, but we do not re-arm the timer (in case it's necessary,
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* tintv.tv64 != 0) until the timer is accessed.
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*/
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static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
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{
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struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr);
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unsigned long flags;
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spin_lock_irqsave(&ctx->wqh.lock, flags);
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ctx->expired = 1;
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ctx->ticks++;
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wake_up_locked(&ctx->wqh);
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spin_unlock_irqrestore(&ctx->wqh.lock, flags);
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return HRTIMER_NORESTART;
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}
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static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
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{
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ktime_t remaining;
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remaining = hrtimer_expires_remaining(&ctx->tmr);
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return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
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}
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static void timerfd_setup(struct timerfd_ctx *ctx, int flags,
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const struct itimerspec *ktmr)
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{
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enum hrtimer_mode htmode;
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ktime_t texp;
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htmode = (flags & TFD_TIMER_ABSTIME) ?
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HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
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texp = timespec_to_ktime(ktmr->it_value);
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ctx->expired = 0;
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ctx->ticks = 0;
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ctx->tintv = timespec_to_ktime(ktmr->it_interval);
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hrtimer_init(&ctx->tmr, ctx->clockid, htmode);
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hrtimer_set_expires(&ctx->tmr, texp);
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ctx->tmr.function = timerfd_tmrproc;
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if (texp.tv64 != 0)
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hrtimer_start(&ctx->tmr, texp, htmode);
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}
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static int timerfd_release(struct inode *inode, struct file *file)
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{
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struct timerfd_ctx *ctx = file->private_data;
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hrtimer_cancel(&ctx->tmr);
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kfree(ctx);
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return 0;
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}
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static unsigned int timerfd_poll(struct file *file, poll_table *wait)
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{
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struct timerfd_ctx *ctx = file->private_data;
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unsigned int events = 0;
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unsigned long flags;
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poll_wait(file, &ctx->wqh, wait);
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spin_lock_irqsave(&ctx->wqh.lock, flags);
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if (ctx->ticks)
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events |= POLLIN;
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spin_unlock_irqrestore(&ctx->wqh.lock, flags);
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return events;
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}
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static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
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loff_t *ppos)
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{
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struct timerfd_ctx *ctx = file->private_data;
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ssize_t res;
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u64 ticks = 0;
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DECLARE_WAITQUEUE(wait, current);
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if (count < sizeof(ticks))
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return -EINVAL;
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spin_lock_irq(&ctx->wqh.lock);
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res = -EAGAIN;
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if (!ctx->ticks && !(file->f_flags & O_NONBLOCK)) {
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__add_wait_queue(&ctx->wqh, &wait);
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for (res = 0;;) {
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set_current_state(TASK_INTERRUPTIBLE);
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if (ctx->ticks) {
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res = 0;
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break;
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}
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if (signal_pending(current)) {
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res = -ERESTARTSYS;
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break;
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}
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spin_unlock_irq(&ctx->wqh.lock);
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schedule();
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spin_lock_irq(&ctx->wqh.lock);
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}
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__remove_wait_queue(&ctx->wqh, &wait);
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__set_current_state(TASK_RUNNING);
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}
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if (ctx->ticks) {
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ticks = ctx->ticks;
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if (ctx->expired && ctx->tintv.tv64) {
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/*
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* If tintv.tv64 != 0, this is a periodic timer that
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* needs to be re-armed. We avoid doing it in the timer
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* callback to avoid DoS attacks specifying a very
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* short timer period.
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*/
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ticks += hrtimer_forward_now(&ctx->tmr,
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ctx->tintv) - 1;
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hrtimer_restart(&ctx->tmr);
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}
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ctx->expired = 0;
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ctx->ticks = 0;
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}
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spin_unlock_irq(&ctx->wqh.lock);
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if (ticks)
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res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
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return res;
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}
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static const struct file_operations timerfd_fops = {
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.release = timerfd_release,
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.poll = timerfd_poll,
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.read = timerfd_read,
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};
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static struct file *timerfd_fget(int fd)
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{
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struct file *file;
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file = fget(fd);
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if (!file)
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return ERR_PTR(-EBADF);
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if (file->f_op != &timerfd_fops) {
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fput(file);
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return ERR_PTR(-EINVAL);
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}
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return file;
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}
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SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
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{
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int ufd;
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struct timerfd_ctx *ctx;
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/* Check the TFD_* constants for consistency. */
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BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
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BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
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if ((flags & ~TFD_CREATE_FLAGS) ||
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(clockid != CLOCK_MONOTONIC &&
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clockid != CLOCK_REALTIME))
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return -EINVAL;
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ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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init_waitqueue_head(&ctx->wqh);
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ctx->clockid = clockid;
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hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
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ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
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flags & TFD_SHARED_FCNTL_FLAGS);
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if (ufd < 0)
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kfree(ctx);
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return ufd;
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}
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SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
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const struct itimerspec __user *, utmr,
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struct itimerspec __user *, otmr)
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{
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struct file *file;
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struct timerfd_ctx *ctx;
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struct itimerspec ktmr, kotmr;
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if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
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return -EFAULT;
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if ((flags & ~TFD_SETTIME_FLAGS) ||
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!timespec_valid(&ktmr.it_value) ||
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!timespec_valid(&ktmr.it_interval))
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return -EINVAL;
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file = timerfd_fget(ufd);
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if (IS_ERR(file))
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return PTR_ERR(file);
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ctx = file->private_data;
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/*
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* We need to stop the existing timer before reprogramming
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* it to the new values.
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*/
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for (;;) {
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spin_lock_irq(&ctx->wqh.lock);
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if (hrtimer_try_to_cancel(&ctx->tmr) >= 0)
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break;
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spin_unlock_irq(&ctx->wqh.lock);
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cpu_relax();
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}
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/*
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* If the timer is expired and it's periodic, we need to advance it
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* because the caller may want to know the previous expiration time.
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* We do not update "ticks" and "expired" since the timer will be
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* re-programmed again in the following timerfd_setup() call.
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*/
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if (ctx->expired && ctx->tintv.tv64)
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hrtimer_forward_now(&ctx->tmr, ctx->tintv);
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kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
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kotmr.it_interval = ktime_to_timespec(ctx->tintv);
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/*
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* Re-program the timer to the new value ...
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*/
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timerfd_setup(ctx, flags, &ktmr);
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spin_unlock_irq(&ctx->wqh.lock);
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fput(file);
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if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr)))
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return -EFAULT;
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return 0;
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}
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SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
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{
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struct file *file;
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struct timerfd_ctx *ctx;
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struct itimerspec kotmr;
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file = timerfd_fget(ufd);
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if (IS_ERR(file))
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return PTR_ERR(file);
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ctx = file->private_data;
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spin_lock_irq(&ctx->wqh.lock);
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if (ctx->expired && ctx->tintv.tv64) {
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ctx->expired = 0;
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ctx->ticks +=
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hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1;
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hrtimer_restart(&ctx->tmr);
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}
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kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
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kotmr.it_interval = ktime_to_timespec(ctx->tintv);
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spin_unlock_irq(&ctx->wqh.lock);
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fput(file);
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return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0;
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}
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