// SPDX-License-Identifier: GPL-2.0 /* * fs/signalfd.c * * Copyright (C) 2003 Linus Torvalds * * Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org> * Changed ->read() to return a siginfo strcture instead of signal number. * Fixed locking in ->poll(). * Added sighand-detach notification. * Added fd re-use in sys_signalfd() syscall. * Now using anonymous inode source. * Thanks to Oleg Nesterov for useful code review and suggestions. * More comments and suggestions from Arnd Bergmann. * Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br> * Retrieve multiple signals with one read() call * Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org> * Attach to the sighand only during read() and poll(). */ #include <linux/file.h> #include <linux/poll.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/sched.h> #include <linux/slab.h> #include <linux/kernel.h> #include <linux/signal.h> #include <linux/list.h> #include <linux/anon_inodes.h> #include <linux/signalfd.h> #include <linux/syscalls.h> #include <linux/proc_fs.h> #include <linux/compat.h> void signalfd_cleanup(struct sighand_struct *sighand) { wait_queue_head_t *wqh = &sighand->signalfd_wqh; /* * The lockless check can race with remove_wait_queue() in progress, * but in this case its caller should run under rcu_read_lock() and * sighand_cachep is SLAB_TYPESAFE_BY_RCU, we can safely return. */ if (likely(!waitqueue_active(wqh))) return; /* wait_queue_entry_t->func(POLLFREE) should do remove_wait_queue() */ wake_up_poll(wqh, EPOLLHUP | POLLFREE); } struct signalfd_ctx { sigset_t sigmask; }; static int signalfd_release(struct inode *inode, struct file *file) { kfree(file->private_data); return 0; } static __poll_t signalfd_poll(struct file *file, poll_table *wait) { struct signalfd_ctx *ctx = file->private_data; __poll_t events = 0; poll_wait(file, ¤t->sighand->signalfd_wqh, wait); spin_lock_irq(¤t->sighand->siglock); if (next_signal(¤t->pending, &ctx->sigmask) || next_signal(¤t->signal->shared_pending, &ctx->sigmask)) events |= EPOLLIN; spin_unlock_irq(¤t->sighand->siglock); return events; } /* * Copied from copy_siginfo_to_user() in kernel/signal.c */ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, kernel_siginfo_t const *kinfo) { struct signalfd_siginfo new; BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128); /* * Unused members should be zero ... */ memset(&new, 0, sizeof(new)); /* * If you change siginfo_t structure, please be sure * this code is fixed accordingly. */ new.ssi_signo = kinfo->si_signo; new.ssi_errno = kinfo->si_errno; new.ssi_code = kinfo->si_code; switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) { case SIL_KILL: new.ssi_pid = kinfo->si_pid; new.ssi_uid = kinfo->si_uid; break; case SIL_TIMER: new.ssi_tid = kinfo->si_tid; new.ssi_overrun = kinfo->si_overrun; new.ssi_ptr = (long) kinfo->si_ptr; new.ssi_int = kinfo->si_int; break; case SIL_POLL: new.ssi_band = kinfo->si_band; new.ssi_fd = kinfo->si_fd; break; case SIL_FAULT_BNDERR: case SIL_FAULT_PKUERR: /* * Fall through to the SIL_FAULT case. Both SIL_FAULT_BNDERR * and SIL_FAULT_PKUERR are only generated by faults that * deliver them synchronously to userspace. In case someone * injects one of these signals and signalfd catches it treat * it as SIL_FAULT. */ case SIL_FAULT: new.ssi_addr = (long) kinfo->si_addr; #ifdef __ARCH_SI_TRAPNO new.ssi_trapno = kinfo->si_trapno; #endif break; case SIL_FAULT_MCEERR: new.ssi_addr = (long) kinfo->si_addr; #ifdef __ARCH_SI_TRAPNO new.ssi_trapno = kinfo->si_trapno; #endif new.ssi_addr_lsb = (short) kinfo->si_addr_lsb; break; case SIL_CHLD: new.ssi_pid = kinfo->si_pid; new.ssi_uid = kinfo->si_uid; new.ssi_status = kinfo->si_status; new.ssi_utime = kinfo->si_utime; new.ssi_stime = kinfo->si_stime; break; case SIL_RT: /* * This case catches also the signals queued by sigqueue(). */ new.ssi_pid = kinfo->si_pid; new.ssi_uid = kinfo->si_uid; new.ssi_ptr = (long) kinfo->si_ptr; new.ssi_int = kinfo->si_int; break; case SIL_SYS: new.ssi_call_addr = (long) kinfo->si_call_addr; new.ssi_syscall = kinfo->si_syscall; new.ssi_arch = kinfo->si_arch; break; } if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo))) return -EFAULT; return sizeof(*uinfo); } static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info, int nonblock) { ssize_t ret; DECLARE_WAITQUEUE(wait, current); spin_lock_irq(¤t->sighand->siglock); ret = dequeue_signal(current, &ctx->sigmask, info); switch (ret) { case 0: if (!nonblock) break; ret = -EAGAIN; /* fall through */ default: spin_unlock_irq(¤t->sighand->siglock); return ret; } add_wait_queue(¤t->sighand->signalfd_wqh, &wait); for (;;) { set_current_state(TASK_INTERRUPTIBLE); ret = dequeue_signal(current, &ctx->sigmask, info); if (ret != 0) break; if (signal_pending(current)) { ret = -ERESTARTSYS; break; } spin_unlock_irq(¤t->sighand->siglock); schedule(); spin_lock_irq(¤t->sighand->siglock); } spin_unlock_irq(¤t->sighand->siglock); remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); __set_current_state(TASK_RUNNING); return ret; } /* * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative * error code. The "count" parameter must be at least the size of a * "struct signalfd_siginfo". */ static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct signalfd_ctx *ctx = file->private_data; struct signalfd_siginfo __user *siginfo; int nonblock = file->f_flags & O_NONBLOCK; ssize_t ret, total = 0; kernel_siginfo_t info; count /= sizeof(struct signalfd_siginfo); if (!count) return -EINVAL; siginfo = (struct signalfd_siginfo __user *) buf; do { ret = signalfd_dequeue(ctx, &info, nonblock); if (unlikely(ret <= 0)) break; ret = signalfd_copyinfo(siginfo, &info); if (ret < 0) break; siginfo++; total += ret; nonblock = 1; } while (--count); return total ? total: ret; } #ifdef CONFIG_PROC_FS static void signalfd_show_fdinfo(struct seq_file *m, struct file *f) { struct signalfd_ctx *ctx = f->private_data; sigset_t sigmask; sigmask = ctx->sigmask; signotset(&sigmask); render_sigset_t(m, "sigmask:\t", &sigmask); } #endif static const struct file_operations signalfd_fops = { #ifdef CONFIG_PROC_FS .show_fdinfo = signalfd_show_fdinfo, #endif .release = signalfd_release, .poll = signalfd_poll, .read = signalfd_read, .llseek = noop_llseek, }; static int do_signalfd4(int ufd, sigset_t *mask, int flags) { struct signalfd_ctx *ctx; /* Check the SFD_* constants for consistency. */ BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) return -EINVAL; sigdelsetmask(mask, sigmask(SIGKILL) | sigmask(SIGSTOP)); signotset(mask); if (ufd == -1) { ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); if (!ctx) return -ENOMEM; ctx->sigmask = *mask; /* * When we call this, the initialization must be complete, since * anon_inode_getfd() will install the fd. */ ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); if (ufd < 0) kfree(ctx); } else { struct fd f = fdget(ufd); if (!f.file) return -EBADF; ctx = f.file->private_data; if (f.file->f_op != &signalfd_fops) { fdput(f); return -EINVAL; } spin_lock_irq(¤t->sighand->siglock); ctx->sigmask = *mask; spin_unlock_irq(¤t->sighand->siglock); wake_up(¤t->sighand->signalfd_wqh); fdput(f); } return ufd; } SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, size_t, sizemask, int, flags) { sigset_t mask; if (sizemask != sizeof(sigset_t) || copy_from_user(&mask, user_mask, sizeof(mask))) return -EINVAL; return do_signalfd4(ufd, &mask, flags); } SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, size_t, sizemask) { sigset_t mask; if (sizemask != sizeof(sigset_t) || copy_from_user(&mask, user_mask, sizeof(mask))) return -EINVAL; return do_signalfd4(ufd, &mask, 0); } #ifdef CONFIG_COMPAT static long do_compat_signalfd4(int ufd, const compat_sigset_t __user *user_mask, compat_size_t sigsetsize, int flags) { sigset_t mask; if (sigsetsize != sizeof(compat_sigset_t)) return -EINVAL; if (get_compat_sigset(&mask, user_mask)) return -EFAULT; return do_signalfd4(ufd, &mask, flags); } COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd, const compat_sigset_t __user *, user_mask, compat_size_t, sigsetsize, int, flags) { return do_compat_signalfd4(ufd, user_mask, sigsetsize, flags); } COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd, const compat_sigset_t __user *, user_mask, compat_size_t, sigsetsize) { return do_compat_signalfd4(ufd, user_mask, sigsetsize, 0); } #endif