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![Al Viro](/assets/img/avatar_default.png)
a) none of the callers even looks at inode or file returned by anon_inode_getfd() b) any caller that would try to look at those would be racy, since by the time it returns we might have raced with close() from another thread and that file would be pining for fjords. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
251 lines
6.7 KiB
C
251 lines
6.7 KiB
C
/*
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* fs/signalfd.c
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*
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* Copyright (C) 2003 Linus Torvalds
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*
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* Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>
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* Changed ->read() to return a siginfo strcture instead of signal number.
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* Fixed locking in ->poll().
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* Added sighand-detach notification.
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* Added fd re-use in sys_signalfd() syscall.
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* Now using anonymous inode source.
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* Thanks to Oleg Nesterov for useful code review and suggestions.
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* More comments and suggestions from Arnd Bergmann.
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* Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
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* Retrieve multiple signals with one read() call
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* Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
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* Attach to the sighand only during read() and poll().
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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/signal.h>
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#include <linux/list.h>
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#include <linux/anon_inodes.h>
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#include <linux/signalfd.h>
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#include <linux/syscalls.h>
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struct signalfd_ctx {
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sigset_t sigmask;
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};
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static int signalfd_release(struct inode *inode, struct file *file)
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{
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kfree(file->private_data);
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return 0;
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}
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static unsigned int signalfd_poll(struct file *file, poll_table *wait)
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{
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struct signalfd_ctx *ctx = file->private_data;
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unsigned int events = 0;
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poll_wait(file, ¤t->sighand->signalfd_wqh, wait);
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spin_lock_irq(¤t->sighand->siglock);
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if (next_signal(¤t->pending, &ctx->sigmask) ||
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next_signal(¤t->signal->shared_pending,
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&ctx->sigmask))
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events |= POLLIN;
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spin_unlock_irq(¤t->sighand->siglock);
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return events;
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}
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/*
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* Copied from copy_siginfo_to_user() in kernel/signal.c
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*/
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static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
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siginfo_t const *kinfo)
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{
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long err;
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BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
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/*
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* Unused members should be zero ...
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*/
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err = __clear_user(uinfo, sizeof(*uinfo));
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/*
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* If you change siginfo_t structure, please be sure
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* this code is fixed accordingly.
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*/
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err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
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err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
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err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
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switch (kinfo->si_code & __SI_MASK) {
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case __SI_KILL:
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err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
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err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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break;
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case __SI_TIMER:
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err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
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err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
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err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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break;
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case __SI_POLL:
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err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
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err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
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break;
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case __SI_FAULT:
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err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
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#ifdef __ARCH_SI_TRAPNO
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err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
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#endif
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break;
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case __SI_CHLD:
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err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
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err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
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err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
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err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
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break;
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case __SI_RT: /* This is not generated by the kernel as of now. */
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case __SI_MESGQ: /* But this is */
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err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
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err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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break;
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default:
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/*
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* This case catches also the signals queued by sigqueue().
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*/
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err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
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err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
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err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
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err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
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break;
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}
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return err ? -EFAULT: sizeof(*uinfo);
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}
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static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
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int nonblock)
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{
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ssize_t ret;
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DECLARE_WAITQUEUE(wait, current);
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spin_lock_irq(¤t->sighand->siglock);
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ret = dequeue_signal(current, &ctx->sigmask, info);
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switch (ret) {
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case 0:
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if (!nonblock)
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break;
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ret = -EAGAIN;
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default:
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spin_unlock_irq(¤t->sighand->siglock);
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return ret;
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}
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add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
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for (;;) {
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set_current_state(TASK_INTERRUPTIBLE);
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ret = dequeue_signal(current, &ctx->sigmask, info);
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if (ret != 0)
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break;
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if (signal_pending(current)) {
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ret = -ERESTARTSYS;
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break;
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}
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spin_unlock_irq(¤t->sighand->siglock);
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schedule();
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spin_lock_irq(¤t->sighand->siglock);
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}
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spin_unlock_irq(¤t->sighand->siglock);
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remove_wait_queue(¤t->sighand->signalfd_wqh, &wait);
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__set_current_state(TASK_RUNNING);
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return ret;
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}
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/*
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* Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
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* error code. The "count" parameter must be at least the size of a
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* "struct signalfd_siginfo".
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*/
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static ssize_t signalfd_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 signalfd_ctx *ctx = file->private_data;
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struct signalfd_siginfo __user *siginfo;
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int nonblock = file->f_flags & O_NONBLOCK;
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ssize_t ret, total = 0;
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siginfo_t info;
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count /= sizeof(struct signalfd_siginfo);
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if (!count)
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return -EINVAL;
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siginfo = (struct signalfd_siginfo __user *) buf;
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do {
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ret = signalfd_dequeue(ctx, &info, nonblock);
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if (unlikely(ret <= 0))
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break;
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ret = signalfd_copyinfo(siginfo, &info);
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if (ret < 0)
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break;
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siginfo++;
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total += ret;
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nonblock = 1;
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} while (--count);
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return total ? total: ret;
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}
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static const struct file_operations signalfd_fops = {
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.release = signalfd_release,
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.poll = signalfd_poll,
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.read = signalfd_read,
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};
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asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask)
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{
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sigset_t sigmask;
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struct signalfd_ctx *ctx;
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if (sizemask != sizeof(sigset_t) ||
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copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
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return -EINVAL;
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sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
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signotset(&sigmask);
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if (ufd == -1) {
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ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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ctx->sigmask = sigmask;
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/*
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* When we call this, the initialization must be complete, since
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* anon_inode_getfd() will install the fd.
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*/
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ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx);
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if (ufd < 0)
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kfree(ctx);
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} else {
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struct file *file = fget(ufd);
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if (!file)
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return -EBADF;
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ctx = file->private_data;
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if (file->f_op != &signalfd_fops) {
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fput(file);
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return -EINVAL;
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}
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spin_lock_irq(¤t->sighand->siglock);
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ctx->sigmask = sigmask;
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spin_unlock_irq(¤t->sighand->siglock);
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wake_up(¤t->sighand->signalfd_wqh);
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fput(file);
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}
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return ufd;
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}
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