SSL open.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
*  linux/fs/open.c
*
*  Copyright (C) 1991, 1992  Linus Torvalds
*/

#include <linux/string.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/fsnotify.h>
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/securebits.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/fcntl.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/fs.h>
#include <linux/personality.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/rcupdate.h>
#include <linux/audit.h>
#include <linux/falloc.h>
#include <linux/fs_struct.h>
#include <linux/dnotify.h>
#include <linux/compat.h>
#include <linux/mnt_idmapping.h>
#include <linux/filelock.h>

#include "internal.h"

int do_truncate(struct mnt_idmap *idmap, struct dentry *dentry,
  loff_t length, unsigned int time_attrs, struct file *filp)
{
int ret;
struct iattr newattrs;

/* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
if (length < 0)
  return -EINVAL;

newattrs.ia_size = length;
newattrs.ia_valid = ATTR_SIZE | time_attrs;
if (filp) {
  newattrs.ia_file = filp;
  newattrs.ia_valid |= ATTR_FILE;
}

/* Remove suid, sgid, and file capabilities on truncate too */
ret = dentry_needs_remove_privs(idmap, dentry);
if (ret < 0)
  return ret;
if (ret)
  newattrs.ia_valid |= ret | ATTR_FORCE;

ret = inode_lock_killable(dentry->d_inode);
if (ret)
  return ret;

/* Note any delegations or leases have already been broken: */
ret = notify_change(idmap, dentry, &newattrs, NULL);
inode_unlock(dentry->d_inode);
return ret;
}

int vfs_truncate(const struct path *path, loff_t length)
{
struct mnt_idmap *idmap;
struct inode *inode;
int error;

inode = path->dentry->d_inode;

/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
if (S_ISDIR(inode->i_mode))
  return -EISDIR;
if (!S_ISREG(inode->i_mode))
  return -EINVAL;

idmap = mnt_idmap(path->mnt);
error = inode_permission(idmap, inode, MAY_WRITE);
if (error)
  return error;

error = fsnotify_truncate_perm(path, length);
if (error)
  return error;

error = mnt_want_write(path->mnt);
if (error)
  return error;

error = -EPERM;
if (IS_APPEND(inode))
  goto mnt_drop_write_and_out;

error = get_write_access(inode);
if (error)
  goto mnt_drop_write_and_out;

/*
* Make sure that there are no leases.  get_write_access() protects
* against the truncate racing with a lease-granting setlease().
*/
error = break_lease(inode, O_WRONLY);
if (error)
  goto put_write_and_out;

error = security_path_truncate(path);
if (!error)
  error = do_truncate(idmap, path->dentry, length, 0, NULL);

put_write_and_out:
put_write_access(inode);
mnt_drop_write_and_out:
mnt_drop_write(path->mnt);

return error;
}
EXPORT_SYMBOL_GPL(vfs_truncate);

int do_sys_truncate(const char __user *pathname, loff_t length)
{
unsigned int lookup_flags = LOOKUP_FOLLOW;
struct path path;
int error;

if (length < 0) /* sorry, but loff_t says... */
  return -EINVAL;

retry:
error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
if (!error) {
  error = vfs_truncate(&path, length);
  path_put(&path);
}
if (retry_estale(error, lookup_flags)) {
  lookup_flags |= LOOKUP_REVAL;
  goto retry;
}
return error;
}

SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
{
return do_sys_truncate(path, length);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
{
return do_sys_truncate(path, length);
}
#endif

int do_ftruncate(struct file *file, loff_t length, int small)
{
struct inode *inode;
struct dentry *dentry;
int error;

/* explicitly opened as large or we are on 64-bit box */
if (file->f_flags & O_LARGEFILE)
  small = 0;

dentry = file->f_path.dentry;
inode = dentry->d_inode;
if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
  return -EINVAL;

/* Cannot ftruncate over 2^31 bytes without large file support */
if (small && length > MAX_NON_LFS)
  return -EINVAL;

/* Check IS_APPEND on real upper inode */
if (IS_APPEND(file_inode(file)))
  return -EPERM;

error = security_file_truncate(file);
if (error)
  return error;

error = fsnotify_truncate_perm(&file->f_path, length);
if (error)
  return error;

sb_start_write(inode->i_sb);
error = do_truncate(file_mnt_idmap(file), dentry, length,
       ATTR_MTIME | ATTR_CTIME, file);
sb_end_write(inode->i_sb);

return error;
}

int do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
if (length < 0)
  return -EINVAL;
CLASS(fd, f)(fd);
if (fd_empty(f))
  return -EBADF;

return do_ftruncate(fd_file(f), length, small);
}

SYSCALL_DEFINE2(ftruncate, unsigned int, fd, off_t, length)
{
return do_sys_ftruncate(fd, length, 1);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_off_t, length)
{
return do_sys_ftruncate(fd, length, 1);
}
#endif

/* LFS versions of truncate are only needed on 32 bit machines */
#if BITS_PER_LONG == 32
SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
{
return do_sys_truncate(path, length);
}

SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
{
return do_sys_ftruncate(fd, length, 0);
}
#endif /* BITS_PER_LONG == 32 */

#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_TRUNCATE64)
COMPAT_SYSCALL_DEFINE3(truncate64, const char __user *, pathname,
         compat_arg_u64_dual(length))
{
return ksys_truncate(pathname, compat_arg_u64_glue(length));
}
#endif

#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_FTRUNCATE64)
COMPAT_SYSCALL_DEFINE3(ftruncate64, unsigned int, fd,
         compat_arg_u64_dual(length))
{
return ksys_ftruncate(fd, compat_arg_u64_glue(length));
}
#endif

int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
struct inode *inode = file_inode(file);
int ret;
loff_t sum;

if (offset < 0 || len <= 0)
  return -EINVAL;

if (mode & ~(FALLOC_FL_MODE_MASK | FALLOC_FL_KEEP_SIZE))
  return -EOPNOTSUPP;

/*
* Modes are exclusive, even if that is not obvious from the encoding
* as bit masks and the mix with the flag in the same namespace.
*
* To make things even more complicated, FALLOC_FL_ALLOCATE_RANGE is
* encoded as no bit set.
*/
switch (mode & FALLOC_FL_MODE_MASK) {
case FALLOC_FL_ALLOCATE_RANGE:
case FALLOC_FL_UNSHARE_RANGE:
case FALLOC_FL_ZERO_RANGE:
  break;
case FALLOC_FL_PUNCH_HOLE:
  if (!(mode & FALLOC_FL_KEEP_SIZE))
   return -EOPNOTSUPP;
  break;
case FALLOC_FL_COLLAPSE_RANGE:
case FALLOC_FL_INSERT_RANGE:
case FALLOC_FL_WRITE_ZEROES:
  if (mode & FALLOC_FL_KEEP_SIZE)
   return -EOPNOTSUPP;
  break;
default:
  return -EOPNOTSUPP;
}

if (!(file->f_mode & FMODE_WRITE))
  return -EBADF;

/*
* On append-only files only space preallocation is supported.
*/
if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
  return -EPERM;

if (IS_IMMUTABLE(inode))
  return -EPERM;

/*
* We cannot allow any fallocate operation on an active swapfile
*/
if (IS_SWAPFILE(inode))
  return -ETXTBSY;

/*
* Revalidate the write permissions, in case security policy has
* changed since the files were opened.
*/
ret = security_file_permission(file, MAY_WRITE);
if (ret)
  return ret;

ret = fsnotify_file_area_perm(file, MAY_WRITE, &offset, len);
if (ret)
  return ret;

if (S_ISFIFO(inode->i_mode))
  return -ESPIPE;

if (S_ISDIR(inode->i_mode))
  return -EISDIR;

if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
  return -ENODEV;

/* Check for wraparound */
if (check_add_overflow(offset, len, &sum))
  return -EFBIG;

if (sum > inode->i_sb->s_maxbytes)
  return -EFBIG;

if (!file->f_op->fallocate)
  return -EOPNOTSUPP;

file_start_write(file);
ret = file->f_op->fallocate(file, mode, offset, len);

/*
* Create inotify and fanotify events.
*
* To keep the logic simple always create events if fallocate succeeds.
* This implies that events are even created if the file size remains
* unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
*/
if (ret == 0)
  fsnotify_modify(file);

file_end_write(file);
return ret;
}
EXPORT_SYMBOL_GPL(vfs_fallocate);

int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
{
CLASS(fd, f)(fd);

if (fd_empty(f))
  return -EBADF;

return vfs_fallocate(fd_file(f), mode, offset, len);
}

SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
{
return ksys_fallocate(fd, mode, offset, len);
}

#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_FALLOCATE)
COMPAT_SYSCALL_DEFINE6(fallocate, int, fd, int, mode, compat_arg_u64_dual(offset),
         compat_arg_u64_dual(len))
{
return ksys_fallocate(fd, mode, compat_arg_u64_glue(offset),
         compat_arg_u64_glue(len));
}
#endif

/*
* access() needs to use the real uid/gid, not the effective uid/gid.
* We do this by temporarily clearing all FS-related capabilities and
* switching the fsuid/fsgid around to the real ones.
*
* Creating new credentials is expensive, so we try to skip doing it,
* which we can if the result would match what we already got.
*/
static bool access_need_override_creds(int flags)
{
const struct cred *cred;

if (flags & AT_EACCESS)
  return false;

cred = current_cred();
if (!uid_eq(cred->fsuid, cred->uid) ||
     !gid_eq(cred->fsgid, cred->gid))
  return true;

if (!issecure(SECURE_NO_SETUID_FIXUP)) {
  kuid_t root_uid = make_kuid(cred->user_ns, 0);
  if (!uid_eq(cred->uid, root_uid)) {
   if (!cap_isclear(cred->cap_effective))
    return true;
  } else {
   if (!cap_isidentical(cred->cap_effective,
       cred->cap_permitted))
    return true;
  }
}

return false;
}

static const struct cred *access_override_creds(void)
{
struct cred *override_cred;

override_cred = prepare_creds();
if (!override_cred)
  return NULL;

/*
* XXX access_need_override_creds performs checks in hopes of skipping
* this work. Make sure it stays in sync if making any changes in this
* routine.
*/

override_cred->fsuid = override_cred->uid;
override_cred->fsgid = override_cred->gid;

if (!issecure(SECURE_NO_SETUID_FIXUP)) {
  /* Clear the capabilities if we switch to a non-root user */
  kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
  if (!uid_eq(override_cred->uid, root_uid))
   cap_clear(override_cred->cap_effective);
  else
   override_cred->cap_effective =
    override_cred->cap_permitted;
}

/*
* The new set of credentials can *only* be used in
* task-synchronous circumstances, and does not need
* RCU freeing, unless somebody then takes a separate
* reference to it.
*
* NOTE! This is _only_ true because this credential
* is used purely for override_creds() that installs
* it as the subjective cred. Other threads will be
* accessing ->real_cred, not the subjective cred.
*
* If somebody _does_ make a copy of this (using the
* 'get_current_cred()' function), that will clear the
* non_rcu field, because now that other user may be
* expecting RCU freeing. But normal thread-synchronous
* cred accesses will keep things non-racy to avoid RCU
* freeing.
*/
override_cred->non_rcu = 1;
return override_creds(override_cred);
}

static int do_faccessat(int dfd, const char __user *filename, int mode, int flags)
{
struct path path;
struct inode *inode;
int res;
unsigned int lookup_flags = LOOKUP_FOLLOW;
const struct cred *old_cred = NULL;

if (mode & ~S_IRWXO) /* where's F_OK, X_OK, W_OK, R_OK? */
  return -EINVAL;

if (flags & ~(AT_EACCESS | AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
  return -EINVAL;

if (flags & AT_SYMLINK_NOFOLLOW)
  lookup_flags &= ~LOOKUP_FOLLOW;
if (flags & AT_EMPTY_PATH)
  lookup_flags |= LOOKUP_EMPTY;

if (access_need_override_creds(flags)) {
  old_cred = access_override_creds();
  if (!old_cred)
   return -ENOMEM;
}

retry:
res = user_path_at(dfd, filename, lookup_flags, &path);
if (res)
  goto out;

inode = d_backing_inode(path.dentry);

if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
  /*
* MAY_EXEC on regular files is denied if the fs is mounted
* with the "noexec" flag.
*/
  res = -EACCES;
  if (path_noexec(&path))
   goto out_path_release;
}

res = inode_permission(mnt_idmap(path.mnt), inode, mode | MAY_ACCESS);
/* SuS v2 requires we report a read only fs too */
if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
  goto out_path_release;
/*
* This is a rare case where using __mnt_is_readonly()
* is OK without a mnt_want/drop_write() pair.  Since
* no actual write to the fs is performed here, we do
* not need to telegraph to that to anyone.
*
* By doing this, we accept that this access is
* inherently racy and know that the fs may change
* state before we even see this result.
*/
if (__mnt_is_readonly(path.mnt))
  res = -EROFS;

out_path_release:
path_put(&path);
if (retry_estale(res, lookup_flags)) {
  lookup_flags |= LOOKUP_REVAL;
  goto retry;
}
out:
if (old_cred)
  put_cred(revert_creds(old_cred));

return res;
}

SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
{
return do_faccessat(dfd, filename, mode, 0);
}

SYSCALL_DEFINE4(faccessat2, int, dfd, const char __user *, filename, int, mode,
  int, flags)
{
return do_faccessat(dfd, filename, mode, flags);
}

SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
{
return do_faccessat(AT_FDCWD, filename, mode, 0);
}

SYSCALL_DEFINE1(chdir, const char __user *, filename)
{
struct path path;
int error;
unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
retry:
error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
if (error)
  goto out;

error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
if (error)
  goto dput_and_out;

set_fs_pwd(current->fs, &path);

dput_and_out:
path_put(&path);
if (retry_estale(error, lookup_flags)) {
  lookup_flags |= LOOKUP_REVAL;
  goto retry;
}
out:
return error;
}

SYSCALL_DEFINE1(fchdir, unsigned int, fd)
{
CLASS(fd_raw, f)(fd);
int error;

if (fd_empty(f))
  return -EBADF;

if (!d_can_lookup(fd_file(f)->f_path.dentry))
  return -ENOTDIR;

error = file_permission(fd_file(f), MAY_EXEC | MAY_CHDIR);
if (!error)
  set_fs_pwd(current->fs, &fd_file(f)->f_path);
return error;
}

SYSCALL_DEFINE1(chroot, const char __user *, filename)
{
struct path path;
int error;
unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
retry:
error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
if (error)
  goto out;

error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
if (error)
  goto dput_and_out;

error = -EPERM;
if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
  goto dput_and_out;
error = security_path_chroot(&path);
if (error)
  goto dput_and_out;

set_fs_root(current->fs, &path);
error = 0;
dput_and_out:
path_put(&path);
if (retry_estale(error, lookup_flags)) {
  lookup_flags |= LOOKUP_REVAL;
  goto retry;
}
out:
return error;
}

int chmod_common(const struct path *path, umode_t mode)
{
struct inode *inode = path->dentry->d_inode;
struct inode *delegated_inode = NULL;
struct iattr newattrs;
int error;

error = mnt_want_write(path->mnt);
if (error)
  return error;
retry_deleg:
error = inode_lock_killable(inode);
if (error)
  goto out_mnt_unlock;
error = security_path_chmod(path, mode);
if (error)
  goto out_unlock;
newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
error = notify_change(mnt_idmap(path->mnt), path->dentry,
         &newattrs, &delegated_inode);
out_unlock:
inode_unlock(inode);
if (delegated_inode) {
  error = break_deleg_wait(&delegated_inode);
  if (!error)
   goto retry_deleg;
}
out_mnt_unlock:
mnt_drop_write(path->mnt);
return error;
}

int vfs_fchmod(struct file *file, umode_t mode)
{
audit_file(file);
return chmod_common(&file->f_path, mode);
}

SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
{
CLASS(fd, f)(fd);

if (fd_empty(f))
  return -EBADF;

return vfs_fchmod(fd_file(f), mode);
}

static int do_fchmodat(int dfd, const char __user *filename, umode_t mode,
         unsigned int flags)
{
struct path path;
int error;
unsigned int lookup_flags;

if (unlikely(flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)))
  return -EINVAL;

lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
if (flags & AT_EMPTY_PATH)
  lookup_flags |= LOOKUP_EMPTY;

retry:
error = user_path_at(dfd, filename, lookup_flags, &path);
if (!error) {
  error = chmod_common(&path, mode);
  path_put(&path);
  if (retry_estale(error, lookup_flags)) {
   lookup_flags |= LOOKUP_REVAL;
   goto retry;
  }
}
return error;
}

SYSCALL_DEFINE4(fchmodat2, int, dfd, const char __user *, filename,
  umode_t, mode, unsigned int, flags)
{
return do_fchmodat(dfd, filename, mode, flags);
}

SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
  umode_t, mode)
{
return do_fchmodat(dfd, filename, mode, 0);
}

SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
{
return do_fchmodat(AT_FDCWD, filename, mode, 0);
}

/*
* Check whether @kuid is valid and if so generate and set vfsuid_t in
* ia_vfsuid.
*
* Return: true if @kuid is valid, false if not.
*/
static inline bool setattr_vfsuid(struct iattr *attr, kuid_t kuid)
{
if (!uid_valid(kuid))
  return false;
attr->ia_valid |= ATTR_UID;
attr->ia_vfsuid = VFSUIDT_INIT(kuid);
return true;
}

/*
* Check whether @kgid is valid and if so generate and set vfsgid_t in
* ia_vfsgid.
*
* Return: true if @kgid is valid, false if not.
*/
static inline bool setattr_vfsgid(struct iattr *attr, kgid_t kgid)
{
if (!gid_valid(kgid))
  return false;
attr->ia_valid |= ATTR_GID;
attr->ia_vfsgid = VFSGIDT_INIT(kgid);
return true;
}

int chown_common(const struct path *path, uid_t user, gid_t group)
{
struct mnt_idmap *idmap;
struct user_namespace *fs_userns;
struct inode *inode = path->dentry->d_inode;
struct inode *delegated_inode = NULL;
int error;
struct iattr newattrs;
kuid_t uid;
kgid_t gid;

uid = make_kuid(current_user_ns(), user);
gid = make_kgid(current_user_ns(), group);

idmap = mnt_idmap(path->mnt);
fs_userns = i_user_ns(inode);

retry_deleg:
newattrs.ia_vfsuid = INVALID_VFSUID;
newattrs.ia_vfsgid = INVALID_VFSGID;
newattrs.ia_valid =  ATTR_CTIME;
if ((user != (uid_t)-1) && !setattr_vfsuid(&newattrs, uid))
  return -EINVAL;
if ((group != (gid_t)-1) && !setattr_vfsgid(&newattrs, gid))
  return -EINVAL;
error = inode_lock_killable(inode);
if (error)
  return error;
if (!S_ISDIR(inode->i_mode))
  newattrs.ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV |
         setattr_should_drop_sgid(idmap, inode);
/* Continue to send actual fs values, not the mount values. */
error = security_path_chown(
  path,
  from_vfsuid(idmap, fs_userns, newattrs.ia_vfsuid),
  from_vfsgid(idmap, fs_userns, newattrs.ia_vfsgid));
if (!error)
  error = notify_change(idmap, path->dentry, &newattrs,
          &delegated_inode);
inode_unlock(inode);
if (delegated_inode) {
  error = break_deleg_wait(&delegated_inode);
  if (!error)
   goto retry_deleg;
}
return error;
}

int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
  int flag)
{
struct path path;
int error = -EINVAL;
int lookup_flags;

if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
  goto out;

lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
if (flag & AT_EMPTY_PATH)
  lookup_flags |= LOOKUP_EMPTY;
retry:
error = user_path_at(dfd, filename, lookup_flags, &path);
if (error)
  goto out;
error = mnt_want_write(path.mnt);
if (error)
  goto out_release;
error = chown_common(&path, user, group);
mnt_drop_write(path.mnt);
out_release:
path_put(&path);
if (retry_estale(error, lookup_flags)) {
  lookup_flags |= LOOKUP_REVAL;
  goto retry;
}
out:
return error;
}

SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
  gid_t, group, int, flag)
{
return do_fchownat(dfd, filename, user, group, flag);
}

SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
{
return do_fchownat(AT_FDCWD, filename, user, group, 0);
}

SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
{
return do_fchownat(AT_FDCWD, filename, user, group,
      AT_SYMLINK_NOFOLLOW);
}

int vfs_fchown(struct file *file, uid_t user, gid_t group)
{
int error;

error = mnt_want_write_file(file);
if (error)
  return error;
audit_file(file);
error = chown_common(&file->f_path, user, group);
mnt_drop_write_file(file);
return error;
}

int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
{
CLASS(fd, f)(fd);

if (fd_empty(f))
  return -EBADF;

return vfs_fchown(fd_file(f), user, group);
}

SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
{
return ksys_fchown(fd, user, group);
}

static inline int file_get_write_access(struct file *f)
{
int error;

error = get_write_access(f->f_inode);
if (unlikely(error))
  return error;
error = mnt_get_write_access(f->f_path.mnt);
if (unlikely(error))
  goto cleanup_inode;
if (unlikely(f->f_mode & FMODE_BACKING)) {
  error = mnt_get_write_access(backing_file_user_path(f)->mnt);
  if (unlikely(error))
   goto cleanup_mnt;
}
return 0;

cleanup_mnt:
mnt_put_write_access(f->f_path.mnt);
cleanup_inode:
put_write_access(f->f_inode);
return error;
}

static int do_dentry_open(struct file *f,
     int (*open)(struct inode *, struct file *))
{
static const struct file_operations empty_fops = {};
struct inode *inode = f->f_path.dentry->d_inode;
int error;

path_get(&f->f_path);
f->f_inode = inode;
f->f_mapping = inode->i_mapping;
f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
f->f_sb_err = file_sample_sb_err(f);

if (unlikely(f->f_flags & O_PATH)) {
  f->f_mode = FMODE_PATH | FMODE_OPENED;
  file_set_fsnotify_mode(f, FMODE_NONOTIFY);
  f->f_op = &empty_fops;
  return 0;
}

if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
  i_readcount_inc(inode);
} else if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
  error = file_get_write_access(f);
  if (unlikely(error))
   goto cleanup_file;
  f->f_mode |= FMODE_WRITER;
}

/* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
  f->f_mode |= FMODE_ATOMIC_POS;

f->f_op = fops_get(inode->i_fop);
if (WARN_ON(!f->f_op)) {
  error = -ENODEV;
  goto cleanup_all;
}

error = security_file_open(f);
if (error)
  goto cleanup_all;

/*
* Call fsnotify open permission hook and set FMODE_NONOTIFY_* bits
* according to existing permission watches.
* If FMODE_NONOTIFY mode was already set for an fanotify fd or for a
* pseudo file, this call will not change the mode.
*/
error = fsnotify_open_perm_and_set_mode(f);
if (error)
  goto cleanup_all;

error = break_lease(file_inode(f), f->f_flags);
if (error)
  goto cleanup_all;

/* normally all 3 are set; ->open() can clear them if needed */
f->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
if (!open)
  open = f->f_op->open;
if (open) {
  error = open(inode, f);
  if (error)
   goto cleanup_all;
}
f->f_mode |= FMODE_OPENED;
if ((f->f_mode & FMODE_READ) &&
      likely(f->f_op->read || f->f_op->read_iter))
  f->f_mode |= FMODE_CAN_READ;
if ((f->f_mode & FMODE_WRITE) &&
      likely(f->f_op->write || f->f_op->write_iter))
  f->f_mode |= FMODE_CAN_WRITE;
if ((f->f_mode & FMODE_LSEEK) && !f->f_op->llseek)
  f->f_mode &= ~FMODE_LSEEK;
if (f->f_mapping->a_ops && f->f_mapping->a_ops->direct_IO)
  f->f_mode |= FMODE_CAN_ODIRECT;

f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
f->f_iocb_flags = iocb_flags(f);

file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);

if ((f->f_flags & O_DIRECT) && !(f->f_mode & FMODE_CAN_ODIRECT))
  return -EINVAL;

/*
* XXX: Huge page cache doesn't support writing yet. Drop all page
* cache for this file before processing writes.
*/
if (f->f_mode & FMODE_WRITE) {
  /*
* Depends on full fence from get_write_access() to synchronize
* against collapse_file() regarding i_writecount and nr_thps
* updates. Ensures subsequent insertion of THPs into the page
* cache will fail.
*/
  if (filemap_nr_thps(inode->i_mapping)) {
   struct address_space *mapping = inode->i_mapping;

   filemap_invalidate_lock(inode->i_mapping);
   /*
* unmap_mapping_range just need to be called once
* here, because the private pages is not need to be
* unmapped mapping (e.g. data segment of dynamic
* shared libraries here).
*/
   unmap_mapping_range(mapping, 0, 0, 0);
   truncate_inode_pages(mapping, 0);
   filemap_invalidate_unlock(inode->i_mapping);
  }
}

return 0;

cleanup_all:
if (WARN_ON_ONCE(error > 0))
  error = -EINVAL;
fops_put(f->f_op);
put_file_access(f);
cleanup_file:
path_put(&f->f_path);
f->f_path.mnt = NULL;
f->f_path.dentry = NULL;
f->f_inode = NULL;
return error;
}

/**
* finish_open - finish opening a file
* @file: file pointer
* @dentry: pointer to dentry
* @open: open callback
*
* This can be used to finish opening a file passed to i_op->atomic_open().
*
* If the open callback is set to NULL, then the standard f_op->open()
* filesystem callback is substituted.
*
* NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
* the return value of d_splice_alias(), then the caller needs to perform dput()
* on it after finish_open().
*
* Returns zero on success or -errno if the open failed.
*/
int finish_open(struct file *file, struct dentry *dentry,
  int (*open)(struct inode *, struct file *))
{
BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */

file->f_path.dentry = dentry;
return do_dentry_open(file, open);
}
EXPORT_SYMBOL(finish_open);

/**
* finish_no_open - finish ->atomic_open() without opening the file
*
* @file: file pointer
* @dentry: dentry, ERR_PTR(-E...) or NULL (as returned from ->lookup())
*
* This can be used to set the result of a lookup in ->atomic_open().
*
* NB: unlike finish_open() this function does consume the dentry reference and
* the caller need not dput() it.
*
* Returns 0 or -E..., which must be the return value of ->atomic_open() after
* having called this function.
*/
int finish_no_open(struct file *file, struct dentry *dentry)
{
if (IS_ERR(dentry))
  return PTR_ERR(dentry);
file->f_path.dentry = dentry;
return 0;
}
EXPORT_SYMBOL(finish_no_open);

char *file_path(struct file *filp, char *buf, int buflen)
{
return d_path(&filp->f_path, buf, buflen);
}
EXPORT_SYMBOL(file_path);

/**
* vfs_open - open the file at the given path
* @path: path to open
* @file: newly allocated file with f_flag initialized
*/
int vfs_open(const struct path *path, struct file *file)
{
int ret;

file->f_path = *path;
ret = do_dentry_open(file, NULL);
if (!ret) {
  /*
* Once we return a file with FMODE_OPENED, __fput() will call
* fsnotify_close(), so we need fsnotify_open() here for
* symmetry.
*/
  fsnotify_open(file);
}
return ret;
}

struct file *dentry_open(const struct path *path, int flags,
    const struct cred *cred)
{
int error;
struct file *f;

/* We must always pass in a valid mount pointer. */
BUG_ON(!path->mnt);

f = alloc_empty_file(flags, cred);
if (!IS_ERR(f)) {
  error = vfs_open(path, f);
  if (error) {
   fput(f);
   f = ERR_PTR(error);
  }
}
return f;
}
EXPORT_SYMBOL(dentry_open);

struct file *dentry_open_nonotify(const struct path *path, int flags,
      const struct cred *cred)
{
struct file *f = alloc_empty_file(flags, cred);
if (!IS_ERR(f)) {
  int error;

  file_set_fsnotify_mode(f, FMODE_NONOTIFY);
  error = vfs_open(path, f);
  if (error) {
   fput(f);
   f = ERR_PTR(error);
  }
}
return f;
}

/**
* dentry_create - Create and open a file
* @path: path to create
* @flags: O_ flags
* @mode: mode bits for new file
* @cred: credentials to use
*
* Caller must hold the parent directory's lock, and have prepared
* a negative dentry, placed in @path->dentry, for the new file.
*
* Caller sets @path->mnt to the vfsmount of the filesystem where
* the new file is to be created. The parent directory and the
* negative dentry must reside on the same filesystem instance.
*
* On success, returns a "struct file *". Otherwise a ERR_PTR
* is returned.
*/
struct file *dentry_create(const struct path *path, int flags, umode_t mode,
      const struct cred *cred)
{
struct file *f;
int error;

f = alloc_empty_file(flags, cred);
if (IS_ERR(f))
  return f;

error = vfs_create(mnt_idmap(path->mnt),
      d_inode(path->dentry->d_parent),
      path->dentry, mode, true);
if (!error)
  error = vfs_open(path, f);

if (unlikely(error)) {
  fput(f);
  return ERR_PTR(error);
}
return f;
}
EXPORT_SYMBOL(dentry_create);

/**
* kernel_file_open - open a file for kernel internal use
* @path: path of the file to open
* @flags: open flags
* @cred: credentials for open
*
* Open a file for use by in-kernel consumers. The file is not accounted
* against nr_files and must not be installed into the file descriptor
* table.
*
* Return: Opened file on success, an error pointer on failure.
*/
struct file *kernel_file_open(const struct path *path, int flags,
    const struct cred *cred)
{
struct file *f;
int error;

f = alloc_empty_file_noaccount(flags, cred);
if (IS_ERR(f))
  return f;

error = vfs_open(path, f);
if (error) {
  fput(f);
  return ERR_PTR(error);
}
return f;
}
EXPORT_SYMBOL_GPL(kernel_file_open);

#define WILL_CREATE(flags) (flags & (O_CREAT | __O_TMPFILE))
#define O_PATH_FLAGS  (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC)

inline struct open_how build_open_how(int flags, umode_t mode)
{
struct open_how how = {
  .flags = flags & VALID_OPEN_FLAGS,
  .mode = mode & S_IALLUGO,
};

/* O_PATH beats everything else. */
if (how.flags & O_PATH)
  how.flags &= O_PATH_FLAGS;
/* Modes should only be set for create-like flags. */
if (!WILL_CREATE(how.flags))
  how.mode = 0;
return how;
}

inline int build_open_flags(const struct open_how *how, struct open_flags *op)
{
u64 flags = how->flags;
u64 strip = O_CLOEXEC;
int lookup_flags = 0;
int acc_mode = ACC_MODE(flags);

BUILD_BUG_ON_MSG(upper_32_bits(VALID_OPEN_FLAGS),
    "struct open_flags doesn't yet handle flags > 32 bits");

/*
* Strip flags that aren't relevant in determining struct open_flags.
*/
flags &= ~strip;

/*
* Older syscalls implicitly clear all of the invalid flags or argument
* values before calling build_open_flags(), but openat2(2) checks all
* of its arguments.
*/
if (flags & ~VALID_OPEN_FLAGS)
  return -EINVAL;
if (how->resolve & ~VALID_RESOLVE_FLAGS)
  return -EINVAL;

/* Scoping flags are mutually exclusive. */
if ((how->resolve & RESOLVE_BENEATH) && (how->resolve & RESOLVE_IN_ROOT))
  return -EINVAL;

/* Deal with the mode. */
if (WILL_CREATE(flags)) {
  if (how->mode & ~S_IALLUGO)
   return -EINVAL;
  op->mode = how->mode | S_IFREG;
} else {
  if (how->mode != 0)
   return -EINVAL;
  op->mode = 0;
}

/*
* Block bugs where O_DIRECTORY | O_CREAT created regular files.
* Note, that blocking O_DIRECTORY | O_CREAT here also protects
* O_TMPFILE below which requires O_DIRECTORY being raised.
*/
if ((flags & (O_DIRECTORY | O_CREAT)) == (O_DIRECTORY | O_CREAT))
  return -EINVAL;

/* Now handle the creative implementation of O_TMPFILE. */
if (flags & __O_TMPFILE) {
  /*
* In order to ensure programs get explicit errors when trying
* to use O_TMPFILE on old kernels we enforce that O_DIRECTORY
* is raised alongside __O_TMPFILE.
*/
  if (!(flags & O_DIRECTORY))
   return -EINVAL;
  if (!(acc_mode & MAY_WRITE))
   return -EINVAL;
}
if (flags & O_PATH) {
  /* O_PATH only permits certain other flags to be set. */
  if (flags & ~O_PATH_FLAGS)
   return -EINVAL;
  acc_mode = 0;
}

/*
* O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
* check for O_DSYNC if the need any syncing at all we enforce it's
* always set instead of having to deal with possibly weird behaviour
* for malicious applications setting only __O_SYNC.
*/
if (flags & __O_SYNC)
  flags |= O_DSYNC;

op->open_flag = flags;

/* O_TRUNC implies we need access checks for write permissions */
if (flags & O_TRUNC)
  acc_mode |= MAY_WRITE;

/* Allow the LSM permission hook to distinguish append
   access from general write access. */
if (flags & O_APPEND)
  acc_mode |= MAY_APPEND;

op->acc_mode = acc_mode;

op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;

if (flags & O_CREAT) {
  op->intent |= LOOKUP_CREATE;
  if (flags & O_EXCL) {
   op->intent |= LOOKUP_EXCL;
   flags |= O_NOFOLLOW;
  }
}

if (flags & O_DIRECTORY)
  lookup_flags |= LOOKUP_DIRECTORY;
if (!(flags & O_NOFOLLOW))
  lookup_flags |= LOOKUP_FOLLOW;

if (how->resolve & RESOLVE_NO_XDEV)
  lookup_flags |= LOOKUP_NO_XDEV;
if (how->resolve & RESOLVE_NO_MAGICLINKS)
  lookup_flags |= LOOKUP_NO_MAGICLINKS;
if (how->resolve & RESOLVE_NO_SYMLINKS)
  lookup_flags |= LOOKUP_NO_SYMLINKS;
if (how->resolve & RESOLVE_BENEATH)
  lookup_flags |= LOOKUP_BENEATH;
if (how->resolve & RESOLVE_IN_ROOT)
  lookup_flags |= LOOKUP_IN_ROOT;
if (how->resolve & RESOLVE_CACHED) {
  /* Don't bother even trying for create/truncate/tmpfile open */
  if (flags & (O_TRUNC | O_CREAT | __O_TMPFILE))
   return -EAGAIN;
  lookup_flags |= LOOKUP_CACHED;
}

op->lookup_flags = lookup_flags;
return 0;
}

/**
* file_open_name - open file and return file pointer
*
* @name: struct filename containing path to open
* @flags: open flags as per the open(2) second argument
* @mode: mode for the new file if O_CREAT is set, else ignored
*
* This is the helper to open a file from kernelspace if you really
* have to.  But in generally you should not do this, so please move
* along, nothing to see here..
*/
struct file *file_open_name(struct filename *name, int flags, umode_t mode)
{
struct open_flags op;
struct open_how how = build_open_how(flags, mode);
int err = build_open_flags(&how, &op);
if (err)
  return ERR_PTR(err);
return do_filp_open(AT_FDCWD, name, &op);
}

/**
* filp_open - open file and return file pointer
*
* @filename: path to open
* @flags: open flags as per the open(2) second argument
* @mode: mode for the new file if O_CREAT is set, else ignored
*
* This is the helper to open a file from kernelspace if you really
* have to.  But in generally you should not do this, so please move
* along, nothing to see here..
*/
struct file *filp_open(const char *filename, int flags, umode_t mode)
{
struct filename *name = getname_kernel(filename);
struct file *file = ERR_CAST(name);

if (!IS_ERR(name)) {
  file = file_open_name(name, flags, mode);
  putname(name);
}
return file;
}
EXPORT_SYMBOL(filp_open);

struct file *file_open_root(const struct path *root,
       const char *filename, int flags, umode_t mode)
{
struct open_flags op;
struct open_how how = build_open_how(flags, mode);
int err = build_open_flags(&how, &op);
if (err)
  return ERR_PTR(err);
return do_file_open_root(root, filename, &op);
}
EXPORT_SYMBOL(file_open_root);

static int do_sys_openat2(int dfd, const char __user *filename,
     struct open_how *how)
{
struct open_flags op;
struct filename *tmp;
int err, fd;

err = build_open_flags(how, &op);
if (unlikely(err))
  return err;

tmp = getname(filename);
if (IS_ERR(tmp))
  return PTR_ERR(tmp);

fd = get_unused_fd_flags(how->flags);
if (likely(fd >= 0)) {
  struct file *f = do_filp_open(dfd, tmp, &op);
  if (IS_ERR(f)) {
   put_unused_fd(fd);
   fd = PTR_ERR(f);
  } else {
   fd_install(fd, f);
  }
}
putname(tmp);
return fd;
}

int do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
{
struct open_how how = build_open_how(flags, mode);
return do_sys_openat2(dfd, filename, &how);
}

SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
if (force_o_largefile())
  flags |= O_LARGEFILE;
return do_sys_open(AT_FDCWD, filename, flags, mode);
}

SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
  umode_t, mode)
{
if (force_o_largefile())
  flags |= O_LARGEFILE;
return do_sys_open(dfd, filename, flags, mode);
}

SYSCALL_DEFINE4(openat2, int, dfd, const char __user *, filename,
  struct open_how __user *, how, size_t, usize)
{
int err;
struct open_how tmp;

BUILD_BUG_ON(sizeof(struct open_how) < OPEN_HOW_SIZE_VER0);
BUILD_BUG_ON(sizeof(struct open_how) != OPEN_HOW_SIZE_LATEST);

if (unlikely(usize < OPEN_HOW_SIZE_VER0))
  return -EINVAL;
if (unlikely(usize > PAGE_SIZE))
  return -E2BIG;

err = copy_struct_from_user(&tmp, sizeof(tmp), how, usize);
if (err)
  return err;

audit_openat2_how(&tmp);

/* O_LARGEFILE is only allowed for non-O_PATH. */
if (!(tmp.flags & O_PATH) && force_o_largefile())
  tmp.flags |= O_LARGEFILE;

return do_sys_openat2(dfd, filename, &tmp);
}

#ifdef CONFIG_COMPAT
/*
* Exactly like sys_open(), except that it doesn't set the
* O_LARGEFILE flag.
*/
COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
return do_sys_open(AT_FDCWD, filename, flags, mode);
}

/*
* Exactly like sys_openat(), except that it doesn't set the
* O_LARGEFILE flag.
*/
COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
{
return do_sys_open(dfd, filename, flags, mode);
}
#endif

#ifndef __alpha__

/*
* For backward compatibility?  Maybe this should be moved
* into arch/i386 instead?
*/
SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
{
int flags = O_CREAT | O_WRONLY | O_TRUNC;

if (force_o_largefile())
  flags |= O_LARGEFILE;
return do_sys_open(AT_FDCWD, pathname, flags, mode);
}
#endif

/*
* "id" is the POSIX thread ID. We use the
* files pointer for this..
*/
static int filp_flush(struct file *filp, fl_owner_t id)
{
int retval = 0;

if (CHECK_DATA_CORRUPTION(file_count(filp) == 0, filp,
   "VFS: Close: file count is 0 (f_op=%ps)",
   filp->f_op)) {
  return 0;
}

if (filp->f_op->flush)
  retval = filp->f_op->flush(filp, id);

if (likely(!(filp->f_mode & FMODE_PATH))) {
  dnotify_flush(filp, id);
  locks_remove_posix(filp, id);
}
return retval;
}

int filp_close(struct file *filp, fl_owner_t id)
{
int retval;

retval = filp_flush(filp, id);
fput_close(filp);

return retval;
}
EXPORT_SYMBOL(filp_close);

/*
* Careful here! We test whether the file pointer is NULL before
* releasing the fd. This ensures that one clone task can't release
* an fd while another clone is opening it.
*/
SYSCALL_DEFINE1(close, unsigned int, fd)
{
int retval;
struct file *file;

file = file_close_fd(fd);
if (!file)
  return -EBADF;

retval = filp_flush(file, current->files);

/*
* We're returning to user space. Don't bother
* with any delayed fput() cases.
*/
fput_close_sync(file);

if (likely(retval == 0))
  return 0;

/* can't restart close syscall because file table entry was cleared */
if (retval == -ERESTARTSYS ||
     retval == -ERESTARTNOINTR ||
     retval == -ERESTARTNOHAND ||
     retval == -ERESTART_RESTARTBLOCK)
  retval = -EINTR;

return retval;
}

/*
* This routine simulates a hangup on the tty, to arrange that users
* are given clean terminals at login time.
*/
SYSCALL_DEFINE0(vhangup)
{
if (capable(CAP_SYS_TTY_CONFIG)) {
  tty_vhangup_self();
  return 0;
}
return -EPERM;
}

/*
* Called when an inode is about to be open.
* We use this to disallow opening large files on 32bit systems if
* the caller didn't specify O_LARGEFILE.  On 64bit systems we force
* on this flag in sys_open.
*/
int generic_file_open(struct inode * inode, struct file * filp)
{
if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
  return -EOVERFLOW;
return 0;
}

EXPORT_SYMBOL(generic_file_open);

/*
* This is used by subsystems that don't want seekable
* file descriptors. The function is not supposed to ever fail, the only
* reason it returns an 'int' and not 'void' is so that it can be plugged
* directly into file_operations structure.
*/
int nonseekable_open(struct inode *inode, struct file *filp)
{
filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
return 0;
}

EXPORT_SYMBOL(nonseekable_open);

/*
* stream_open is used by subsystems that want stream-like file descriptors.
* Such file descriptors are not seekable and don't have notion of position
* (file.f_pos is always 0 and ppos passed to .read()/.write() is always NULL).
* Contrary to file descriptors of other regular files, .read() and .write()
* can run simultaneously.
*
* stream_open never fails and is marked to return int so that it could be
* directly used as file_operations.open .
*/
int stream_open(struct inode *inode, struct file *filp)
{
filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE | FMODE_ATOMIC_POS);
filp->f_mode |= FMODE_STREAM;
return 0;
}

EXPORT_SYMBOL(stream_open);

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