/* * linux/fs/fcntl.c * * Copyright (C) 1991, 1992 Linus Torvalds */ #include <linux/syscalls.h> #include <linux/init.h> #include <linux/mm.h> #include <linux/fs.h> #include <linux/file.h> #include <linux/fdtable.h> #include <linux/capability.h> #include <linux/dnotify.h> #include <linux/slab.h> #include <linux/module.h> #include <linux/security.h> #include <linux/ptrace.h> #include <linux/signal.h> #include <linux/rcupdate.h> #include <linux/pid_namespace.h> #include <asm/poll.h> #include <asm/siginfo.h> #include <asm/uaccess.h> void set_close_on_exec(unsigned int fd, int flag) { struct files_struct *files = current->files; struct fdtable *fdt; spin_lock(&files->file_lock); fdt = files_fdtable(files); if (flag) FD_SET(fd, fdt->close_on_exec); else FD_CLR(fd, fdt->close_on_exec); spin_unlock(&files->file_lock); } static int get_close_on_exec(unsigned int fd) { struct files_struct *files = current->files; struct fdtable *fdt; int res; rcu_read_lock(); fdt = files_fdtable(files); res = FD_ISSET(fd, fdt->close_on_exec); rcu_read_unlock(); return res; } SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) { int err = -EBADF; struct file * file, *tofree; struct files_struct * files = current->files; struct fdtable *fdt; if ((flags & ~O_CLOEXEC) != 0) return -EINVAL; if (unlikely(oldfd == newfd)) return -EINVAL; spin_lock(&files->file_lock); err = expand_files(files, newfd); file = fcheck(oldfd); if (unlikely(!file)) goto Ebadf; if (unlikely(err < 0)) { if (err == -EMFILE) goto Ebadf; goto out_unlock; } /* * We need to detect attempts to do dup2() over allocated but still * not finished descriptor. NB: OpenBSD avoids that at the price of * extra work in their equivalent of fget() - they insert struct * file immediately after grabbing descriptor, mark it larval if * more work (e.g. actual opening) is needed and make sure that * fget() treats larval files as absent. Potentially interesting, * but while extra work in fget() is trivial, locking implications * and amount of surgery on open()-related paths in VFS are not. * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" * deadlocks in rather amusing ways, AFAICS. All of that is out of * scope of POSIX or SUS, since neither considers shared descriptor * tables and this condition does not arise without those. */ err = -EBUSY; fdt = files_fdtable(files); tofree = fdt->fd[newfd]; if (!tofree && FD_ISSET(newfd, fdt->open_fds)) goto out_unlock; get_file(file); rcu_assign_pointer(fdt->fd[newfd], file); FD_SET(newfd, fdt->open_fds); if (flags & O_CLOEXEC) FD_SET(newfd, fdt->close_on_exec); else FD_CLR(newfd, fdt->close_on_exec); spin_unlock(&files->file_lock); if (tofree) filp_close(tofree, files); return newfd; Ebadf: err = -EBADF; out_unlock: spin_unlock(&files->file_lock); return err; } SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) { if (unlikely(newfd == oldfd)) { /* corner case */ struct files_struct *files = current->files; int retval = oldfd; rcu_read_lock(); if (!fcheck_files(files, oldfd)) retval = -EBADF; rcu_read_unlock(); return retval; } return sys_dup3(oldfd, newfd, 0); } SYSCALL_DEFINE1(dup, unsigned int, fildes) { int ret = -EBADF; struct file *file = fget(fildes); if (file) { ret = get_unused_fd(); if (ret >= 0) fd_install(ret, file); else fput(file); } return ret; } #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME) static int setfl(int fd, struct file * filp, unsigned long arg) { struct inode * inode = filp->f_path.dentry->d_inode; int error = 0; /* * O_APPEND cannot be cleared if the file is marked as append-only * and the file is open for write. */ if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode)) return -EPERM; /* O_NOATIME can only be set by the owner or superuser */ if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME)) if (!is_owner_or_cap(inode)) return -EPERM; /* required for strict SunOS emulation */ if (O_NONBLOCK != O_NDELAY) if (arg & O_NDELAY) arg |= O_NONBLOCK; if (arg & O_DIRECT) { if (!filp->f_mapping || !filp->f_mapping->a_ops || !filp->f_mapping->a_ops->direct_IO) return -EINVAL; } if (filp->f_op && filp->f_op->check_flags) error = filp->f_op->check_flags(arg); if (error) return error; /* * ->fasync() is responsible for setting the FASYNC bit. */ if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op && filp->f_op->fasync) { error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0); if (error < 0) goto out; if (error > 0) error = 0; } spin_lock(&filp->f_lock); filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK); spin_unlock(&filp->f_lock); out: return error; } static void f_modown(struct file *filp, struct pid *pid, enum pid_type type, int force) { write_lock_irq(&filp->f_owner.lock); if (force || !filp->f_owner.pid) { put_pid(filp->f_owner.pid); filp->f_owner.pid = get_pid(pid); filp->f_owner.pid_type = type; if (pid) { const struct cred *cred = current_cred(); filp->f_owner.uid = cred->uid; filp->f_owner.euid = cred->euid; } } write_unlock_irq(&filp->f_owner.lock); } int __f_setown(struct file *filp, struct pid *pid, enum pid_type type, int force) { int err; err = security_file_set_fowner(filp); if (err) return err; f_modown(filp, pid, type, force); return 0; } EXPORT_SYMBOL(__f_setown); int f_setown(struct file *filp, unsigned long arg, int force) { enum pid_type type; struct pid *pid; int who = arg; int result; type = PIDTYPE_PID; if (who < 0) { type = PIDTYPE_PGID; who = -who; } rcu_read_lock(); pid = find_vpid(who); result = __f_setown(filp, pid, type, force); rcu_read_unlock(); return result; } EXPORT_SYMBOL(f_setown); void f_delown(struct file *filp) { f_modown(filp, NULL, PIDTYPE_PID, 1); } pid_t f_getown(struct file *filp) { pid_t pid; read_lock(&filp->f_owner.lock); pid = pid_vnr(filp->f_owner.pid); if (filp->f_owner.pid_type == PIDTYPE_PGID) pid = -pid; read_unlock(&filp->f_owner.lock); return pid; } static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, struct file *filp) { long err = -EINVAL; switch (cmd) { case F_DUPFD: case F_DUPFD_CLOEXEC: if (arg >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur) break; err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0); if (err >= 0) { get_file(filp); fd_install(err, filp); } break; case F_GETFD: err = get_close_on_exec(fd) ? FD_CLOEXEC : 0; break; case F_SETFD: err = 0; set_close_on_exec(fd, arg & FD_CLOEXEC); break; case F_GETFL: err = filp->f_flags; break; case F_SETFL: err = setfl(fd, filp, arg); break; case F_GETLK: err = fcntl_getlk(filp, (struct flock __user *) arg); break; case F_SETLK: case F_SETLKW: err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg); break; case F_GETOWN: /* * XXX If f_owner is a process group, the * negative return value will get converted * into an error. Oops. If we keep the * current syscall conventions, the only way * to fix this will be in libc. */ err = f_getown(filp); force_successful_syscall_return(); break; case F_SETOWN: err = f_setown(filp, arg, 1); break; case F_GETSIG: err = filp->f_owner.signum; break; case F_SETSIG: /* arg == 0 restores default behaviour. */ if (!valid_signal(arg)) { break; } err = 0; filp->f_owner.signum = arg; break; case F_GETLEASE: err = fcntl_getlease(filp); break; case F_SETLEASE: err = fcntl_setlease(fd, filp, arg); break; case F_NOTIFY: err = fcntl_dirnotify(fd, filp, arg); break; default: break; } return err; } SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg) { struct file *filp; long err = -EBADF; filp = fget(fd); if (!filp) goto out; err = security_file_fcntl(filp, cmd, arg); if (err) { fput(filp); return err; } err = do_fcntl(fd, cmd, arg, filp); fput(filp); out: return err; } #if BITS_PER_LONG == 32 SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd, unsigned long, arg) { struct file * filp; long err; err = -EBADF; filp = fget(fd); if (!filp) goto out; err = security_file_fcntl(filp, cmd, arg); if (err) { fput(filp); return err; } err = -EBADF; switch (cmd) { case F_GETLK64: err = fcntl_getlk64(filp, (struct flock64 __user *) arg); break; case F_SETLK64: case F_SETLKW64: err = fcntl_setlk64(fd, filp, cmd, (struct flock64 __user *) arg); break; default: err = do_fcntl(fd, cmd, arg, filp); break; } fput(filp); out: return err; } #endif /* Table to convert sigio signal codes into poll band bitmaps */ static const long band_table[NSIGPOLL] = { POLLIN | POLLRDNORM, /* POLL_IN */ POLLOUT | POLLWRNORM | POLLWRBAND, /* POLL_OUT */ POLLIN | POLLRDNORM | POLLMSG, /* POLL_MSG */ POLLERR, /* POLL_ERR */ POLLPRI | POLLRDBAND, /* POLL_PRI */ POLLHUP | POLLERR /* POLL_HUP */ }; static inline int sigio_perm(struct task_struct *p, struct fown_struct *fown, int sig) { const struct cred *cred; int ret; rcu_read_lock(); cred = __task_cred(p); ret = ((fown->euid == 0 || fown->euid == cred->suid || fown->euid == cred->uid || fown->uid == cred->suid || fown->uid == cred->uid) && !security_file_send_sigiotask(p, fown, sig)); rcu_read_unlock(); return ret; } static void send_sigio_to_task(struct task_struct *p, struct fown_struct *fown, int fd, int reason) { /* * F_SETSIG can change ->signum lockless in parallel, make * sure we read it once and use the same value throughout. */ int signum = ACCESS_ONCE(fown->signum); if (!sigio_perm(p, fown, signum)) return; switch (signum) { siginfo_t si; default: /* Queue a rt signal with the appropriate fd as its value. We use SI_SIGIO as the source, not SI_KERNEL, since kernel signals always get delivered even if we can't queue. Failure to queue in this case _should_ be reported; we fall back to SIGIO in that case. --sct */ si.si_signo = signum; si.si_errno = 0; si.si_code = reason; /* Make sure we are called with one of the POLL_* reasons, otherwise we could leak kernel stack into userspace. */ BUG_ON((reason & __SI_MASK) != __SI_POLL); if (reason - POLL_IN >= NSIGPOLL) si.si_band = ~0L; else si.si_band = band_table[reason - POLL_IN]; si.si_fd = fd; if (!group_send_sig_info(signum, &si, p)) break; /* fall-through: fall back on the old plain SIGIO signal */ case 0: group_send_sig_info(SIGIO, SEND_SIG_PRIV, p); } } void send_sigio(struct fown_struct *fown, int fd, int band) { struct task_struct *p; enum pid_type type; struct pid *pid; read_lock(&fown->lock); type = fown->pid_type; pid = fown->pid; if (!pid) goto out_unlock_fown; read_lock(&tasklist_lock); do_each_pid_task(pid, type, p) { send_sigio_to_task(p, fown, fd, band); } while_each_pid_task(pid, type, p); read_unlock(&tasklist_lock); out_unlock_fown: read_unlock(&fown->lock); } static void send_sigurg_to_task(struct task_struct *p, struct fown_struct *fown) { if (sigio_perm(p, fown, SIGURG)) group_send_sig_info(SIGURG, SEND_SIG_PRIV, p); } int send_sigurg(struct fown_struct *fown) { struct task_struct *p; enum pid_type type; struct pid *pid; int ret = 0; read_lock(&fown->lock); type = fown->pid_type; pid = fown->pid; if (!pid) goto out_unlock_fown; ret = 1; read_lock(&tasklist_lock); do_each_pid_task(pid, type, p) { send_sigurg_to_task(p, fown); } while_each_pid_task(pid, type, p); read_unlock(&tasklist_lock); out_unlock_fown: read_unlock(&fown->lock); return ret; } static DEFINE_RWLOCK(fasync_lock); static struct kmem_cache *fasync_cache __read_mostly; /* * fasync_helper() is used by almost all character device drivers * to set up the fasync queue. It returns negative on error, 0 if it did * no changes and positive if it added/deleted the entry. */ int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp) { struct fasync_struct *fa, **fp; struct fasync_struct *new = NULL; int result = 0; if (on) { new = kmem_cache_alloc(fasync_cache, GFP_KERNEL); if (!new) return -ENOMEM; } /* * We need to take f_lock first since it's not an IRQ-safe * lock. */ spin_lock(&filp->f_lock); write_lock_irq(&fasync_lock); for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) { if (fa->fa_file == filp) { if(on) { fa->fa_fd = fd; kmem_cache_free(fasync_cache, new); } else { *fp = fa->fa_next; kmem_cache_free(fasync_cache, fa); result = 1; } goto out; } } if (on) { new->magic = FASYNC_MAGIC; new->fa_file = filp; new->fa_fd = fd; new->fa_next = *fapp; *fapp = new; result = 1; } out: if (on) filp->f_flags |= FASYNC; else filp->f_flags &= ~FASYNC; write_unlock_irq(&fasync_lock); spin_unlock(&filp->f_lock); return result; } EXPORT_SYMBOL(fasync_helper); void __kill_fasync(struct fasync_struct *fa, int sig, int band) { while (fa) { struct fown_struct * fown; if (fa->magic != FASYNC_MAGIC) { printk(KERN_ERR "kill_fasync: bad magic number in " "fasync_struct!\n"); return; } fown = &fa->fa_file->f_owner; /* Don't send SIGURG to processes which have not set a queued signum: SIGURG has its own default signalling mechanism. */ if (!(sig == SIGURG && fown->signum == 0)) send_sigio(fown, fa->fa_fd, band); fa = fa->fa_next; } } EXPORT_SYMBOL(__kill_fasync); void kill_fasync(struct fasync_struct **fp, int sig, int band) { /* First a quick test without locking: usually * the list is empty. */ if (*fp) { read_lock(&fasync_lock); /* reread *fp after obtaining the lock */ __kill_fasync(*fp, sig, band); read_unlock(&fasync_lock); } } EXPORT_SYMBOL(kill_fasync); static int __init fasync_init(void) { fasync_cache = kmem_cache_create("fasync_cache", sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL); return 0; } module_init(fasync_init)