- 根目录:
- fs
- fcntl.c
/*
* 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/pipe_fs_i.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_raw(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 (!inode_owner_or_capable(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 int f_setown_ex(struct file *filp, unsigned long arg)
{
struct f_owner_ex * __user owner_p = (void * __user)arg;
struct f_owner_ex owner;
struct pid *pid;
int type;
int ret;
ret = copy_from_user(&owner, owner_p, sizeof(owner));
if (ret)
return -EFAULT;
switch (owner.type) {
case F_OWNER_TID:
type = PIDTYPE_MAX;
break;
case F_OWNER_PID:
type = PIDTYPE_PID;
break;
case F_OWNER_PGRP:
type = PIDTYPE_PGID;
break;
default:
return -EINVAL;
}
rcu_read_lock();
pid = find_vpid(owner.pid);
if (owner.pid && !pid)
ret = -ESRCH;
else
ret = __f_setown(filp, pid, type, 1);
rcu_read_unlock();
return ret;
}
static int f_getown_ex(struct file *filp, unsigned long arg)
{
struct f_owner_ex * __user owner_p = (void * __user)arg;
struct f_owner_ex owner;
int ret = 0;
read_lock(&filp->f_owner.lock);
owner.pid = pid_vnr(filp->f_owner.pid);
switch (filp->f_owner.pid_type) {
case PIDTYPE_MAX:
owner.type = F_OWNER_TID;
break;
case PIDTYPE_PID:
owner.type = F_OWNER_PID;
break;
case PIDTYPE_PGID:
owner.type = F_OWNER_PGRP;
break;
default:
WARN_ON(1);
ret = -EINVAL;
break;
}
read_unlock(&filp->f_owner.lock);
if (!ret) {
ret = copy_to_user(owner_p, &owner, sizeof(owner));
if (ret)
ret = -EFAULT;
}
return ret;
}
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 >= rlimit(RLIMIT_NOFILE))
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_GETOWN_EX:
err = f_getown_ex(filp, arg);
break;
case F_SETOWN_EX:
err = f_setown_ex(filp, arg);
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;
case F_SETPIPE_SZ:
case F_GETPIPE_SZ:
err = pipe_fcntl(filp, cmd, arg);
break;
default:
break;
}
return err;
}
static int check_fcntl_cmd(unsigned cmd)
{
switch (cmd) {
case F_DUPFD:
case F_DUPFD_CLOEXEC:
case F_GETFD:
case F_SETFD:
case F_GETFL:
return 1;
}
return 0;
}
SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
{
struct file *filp;
long err = -EBADF;
filp = fget_raw(fd);
if (!filp)
goto out;
if (unlikely(filp->f_mode & FMODE_PATH)) {
if (!check_fcntl_cmd(cmd)) {
fput(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_raw(fd);
if (!filp)
goto out;
if (unlikely(filp->f_mode & FMODE_PATH)) {
if (!check_fcntl_cmd(cmd)) {
fput(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, int group)
{
/*
* 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 (!do_send_sig_info(signum, &si, p, group))
break;
/* fall-through: fall back on the old plain SIGIO signal */
case 0:
do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, group);
}
}
void send_sigio(struct fown_struct *fown, int fd, int band)
{
struct task_struct *p;
enum pid_type type;
struct pid *pid;
int group = 1;
read_lock(&fown->lock);
type = fown->pid_type;
if (type == PIDTYPE_MAX) {
group = 0;
type = PIDTYPE_PID;
}
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, group);
} 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, int group)
{
if (sigio_perm(p, fown, SIGURG))
do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, group);
}
int send_sigurg(struct fown_struct *fown)
{
struct task_struct *p;
enum pid_type type;
struct pid *pid;
int group = 1;
int ret = 0;
read_lock(&fown->lock);
type = fown->pid_type;
if (type == PIDTYPE_MAX) {
group = 0;
type = PIDTYPE_PID;
}
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, group);
} while_each_pid_task(pid, type, p);
read_unlock(&tasklist_lock);
out_unlock_fown:
read_unlock(&fown->lock);
return ret;
}
static DEFINE_SPINLOCK(fasync_lock);
static struct kmem_cache *fasync_cache __read_mostly;
static void fasync_free_rcu(struct rcu_head *head)
{
kmem_cache_free(fasync_cache,
container_of(head, struct fasync_struct, fa_rcu));
}
/*
* Remove a fasync entry. If successfully removed, return
* positive and clear the FASYNC flag. If no entry exists,
* do nothing and return 0.
*
* NOTE! It is very important that the FASYNC flag always
* match the state "is the filp on a fasync list".
*
*/
int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
{
struct fasync_struct *fa, **fp;
int result = 0;
spin_lock(&filp->f_lock);
spin_lock(&fasync_lock);
for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
if (fa->fa_file != filp)
continue;
spin_lock_irq(&fa->fa_lock);
fa->fa_file = NULL;
spin_unlock_irq(&fa->fa_lock);
*fp = fa->fa_next;
call_rcu(&fa->fa_rcu, fasync_free_rcu);
filp->f_flags &= ~FASYNC;
result = 1;
break;
}
spin_unlock(&fasync_lock);
spin_unlock(&filp->f_lock);
return result;
}
struct fasync_struct *fasync_alloc(void)
{
return kmem_cache_alloc(fasync_cache, GFP_KERNEL);
}
/*
* NOTE! This can be used only for unused fasync entries:
* entries that actually got inserted on the fasync list
* need to be released by rcu - see fasync_remove_entry.
*/
void fasync_free(struct fasync_struct *new)
{
kmem_cache_free(fasync_cache, new);
}
/*
* Insert a new entry into the fasync list. Return the pointer to the
* old one if we didn't use the new one.
*
* NOTE! It is very important that the FASYNC flag always
* match the state "is the filp on a fasync list".
*/
struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
{
struct fasync_struct *fa, **fp;
spin_lock(&filp->f_lock);
spin_lock(&fasync_lock);
for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
if (fa->fa_file != filp)
continue;
spin_lock_irq(&fa->fa_lock);
fa->fa_fd = fd;
spin_unlock_irq(&fa->fa_lock);
goto out;
}
spin_lock_init(&new->fa_lock);
new->magic = FASYNC_MAGIC;
new->fa_file = filp;
new->fa_fd = fd;
new->fa_next = *fapp;
rcu_assign_pointer(*fapp, new);
filp->f_flags |= FASYNC;
out:
spin_unlock(&fasync_lock);
spin_unlock(&filp->f_lock);
return fa;
}
/*
* Add a fasync entry. Return negative on error, positive if
* added, and zero if did nothing but change an existing one.
*/
static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
{
struct fasync_struct *new;
new = fasync_alloc();
if (!new)
return -ENOMEM;
/*
* fasync_insert_entry() returns the old (update) entry if
* it existed.
*
* So free the (unused) new entry and return 0 to let the
* caller know that we didn't add any new fasync entries.
*/
if (fasync_insert_entry(fd, filp, fapp, new)) {
fasync_free(new);
return 0;
}
return 1;
}
/*
* fasync_helper() is used by almost all character device drivers
* to set up the fasync queue, and for regular files by the file
* lease code. 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)
{
if (!on)
return fasync_remove_entry(filp, fapp);
return fasync_add_entry(fd, filp, fapp);
}
EXPORT_SYMBOL(fasync_helper);
/*
* rcu_read_lock() is held
*/
static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
{
while (fa) {
struct fown_struct *fown;
unsigned long flags;
if (fa->magic != FASYNC_MAGIC) {
printk(KERN_ERR "kill_fasync: bad magic number in "
"fasync_struct!\n");
return;
}
spin_lock_irqsave(&fa->fa_lock, flags);
if (fa->fa_file) {
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);
}
spin_unlock_irqrestore(&fa->fa_lock, flags);
fa = rcu_dereference(fa->fa_next);
}
}
void kill_fasync(struct fasync_struct **fp, int sig, int band)
{
/* First a quick test without locking: usually
* the list is empty.
*/
if (*fp) {
rcu_read_lock();
kill_fasync_rcu(rcu_dereference(*fp), sig, band);
rcu_read_unlock();
}
}
EXPORT_SYMBOL(kill_fasync);
static int __init fcntl_init(void)
{
/*
* Please add new bits here to ensure allocation uniqueness.
* Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
* is defined as O_NONBLOCK on some platforms and not on others.
*/
BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
O_RDONLY | O_WRONLY | O_RDWR |
O_CREAT | O_EXCL | O_NOCTTY |
O_TRUNC | O_APPEND | /* O_NONBLOCK | */
__O_SYNC | O_DSYNC | FASYNC |
O_DIRECT | O_LARGEFILE | O_DIRECTORY |
O_NOFOLLOW | O_NOATIME | O_CLOEXEC |
__FMODE_EXEC | O_PATH
));
fasync_cache = kmem_cache_create("fasync_cache",
sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
return 0;
}
module_init(fcntl_init)