linux/fs/open.c
David Howells e0e817392b CRED: Add some configurable debugging [try #6]
Add a config option (CONFIG_DEBUG_CREDENTIALS) to turn on some debug checking
for credential management.  The additional code keeps track of the number of
pointers from task_structs to any given cred struct, and checks to see that
this number never exceeds the usage count of the cred struct (which includes
all references, not just those from task_structs).

Furthermore, if SELinux is enabled, the code also checks that the security
pointer in the cred struct is never seen to be invalid.

This attempts to catch the bug whereby inode_has_perm() faults in an nfsd
kernel thread on seeing cred->security be a NULL pointer (it appears that the
credential struct has been previously released):

	http://www.kerneloops.org/oops.php?number=252883

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-09-02 21:29:01 +10:00

1197 lines
27 KiB
C

/*
* 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/quotaops.h>
#include <linux/fsnotify.h>
#include <linux/module.h>
#include <linux/slab.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/vfs.h>
#include <linux/fcntl.h>
#include <asm/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>
int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
int retval = -ENODEV;
if (dentry) {
retval = -ENOSYS;
if (dentry->d_sb->s_op->statfs) {
memset(buf, 0, sizeof(*buf));
retval = security_sb_statfs(dentry);
if (retval)
return retval;
retval = dentry->d_sb->s_op->statfs(dentry, buf);
if (retval == 0 && buf->f_frsize == 0)
buf->f_frsize = buf->f_bsize;
}
}
return retval;
}
EXPORT_SYMBOL(vfs_statfs);
static int vfs_statfs_native(struct dentry *dentry, struct statfs *buf)
{
struct kstatfs st;
int retval;
retval = vfs_statfs(dentry, &st);
if (retval)
return retval;
if (sizeof(*buf) == sizeof(st))
memcpy(buf, &st, sizeof(st));
else {
if (sizeof buf->f_blocks == 4) {
if ((st.f_blocks | st.f_bfree | st.f_bavail |
st.f_bsize | st.f_frsize) &
0xffffffff00000000ULL)
return -EOVERFLOW;
/*
* f_files and f_ffree may be -1; it's okay to stuff
* that into 32 bits
*/
if (st.f_files != -1 &&
(st.f_files & 0xffffffff00000000ULL))
return -EOVERFLOW;
if (st.f_ffree != -1 &&
(st.f_ffree & 0xffffffff00000000ULL))
return -EOVERFLOW;
}
buf->f_type = st.f_type;
buf->f_bsize = st.f_bsize;
buf->f_blocks = st.f_blocks;
buf->f_bfree = st.f_bfree;
buf->f_bavail = st.f_bavail;
buf->f_files = st.f_files;
buf->f_ffree = st.f_ffree;
buf->f_fsid = st.f_fsid;
buf->f_namelen = st.f_namelen;
buf->f_frsize = st.f_frsize;
memset(buf->f_spare, 0, sizeof(buf->f_spare));
}
return 0;
}
static int vfs_statfs64(struct dentry *dentry, struct statfs64 *buf)
{
struct kstatfs st;
int retval;
retval = vfs_statfs(dentry, &st);
if (retval)
return retval;
if (sizeof(*buf) == sizeof(st))
memcpy(buf, &st, sizeof(st));
else {
buf->f_type = st.f_type;
buf->f_bsize = st.f_bsize;
buf->f_blocks = st.f_blocks;
buf->f_bfree = st.f_bfree;
buf->f_bavail = st.f_bavail;
buf->f_files = st.f_files;
buf->f_ffree = st.f_ffree;
buf->f_fsid = st.f_fsid;
buf->f_namelen = st.f_namelen;
buf->f_frsize = st.f_frsize;
memset(buf->f_spare, 0, sizeof(buf->f_spare));
}
return 0;
}
SYSCALL_DEFINE2(statfs, const char __user *, pathname, struct statfs __user *, buf)
{
struct path path;
int error;
error = user_path(pathname, &path);
if (!error) {
struct statfs tmp;
error = vfs_statfs_native(path.dentry, &tmp);
if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
error = -EFAULT;
path_put(&path);
}
return error;
}
SYSCALL_DEFINE3(statfs64, const char __user *, pathname, size_t, sz, struct statfs64 __user *, buf)
{
struct path path;
long error;
if (sz != sizeof(*buf))
return -EINVAL;
error = user_path(pathname, &path);
if (!error) {
struct statfs64 tmp;
error = vfs_statfs64(path.dentry, &tmp);
if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
error = -EFAULT;
path_put(&path);
}
return error;
}
SYSCALL_DEFINE2(fstatfs, unsigned int, fd, struct statfs __user *, buf)
{
struct file * file;
struct statfs tmp;
int error;
error = -EBADF;
file = fget(fd);
if (!file)
goto out;
error = vfs_statfs_native(file->f_path.dentry, &tmp);
if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
error = -EFAULT;
fput(file);
out:
return error;
}
SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, size_t, sz, struct statfs64 __user *, buf)
{
struct file * file;
struct statfs64 tmp;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = -EBADF;
file = fget(fd);
if (!file)
goto out;
error = vfs_statfs64(file->f_path.dentry, &tmp);
if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
error = -EFAULT;
fput(file);
out:
return error;
}
int do_truncate(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 on truncate too */
ret = should_remove_suid(dentry);
if (ret)
newattrs.ia_valid |= ret | ATTR_FORCE;
mutex_lock(&dentry->d_inode->i_mutex);
ret = notify_change(dentry, &newattrs);
mutex_unlock(&dentry->d_inode->i_mutex);
return ret;
}
static long do_sys_truncate(const char __user *pathname, loff_t length)
{
struct path path;
struct inode *inode;
int error;
error = -EINVAL;
if (length < 0) /* sorry, but loff_t says... */
goto out;
error = user_path(pathname, &path);
if (error)
goto out;
inode = path.dentry->d_inode;
/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
error = -EISDIR;
if (S_ISDIR(inode->i_mode))
goto dput_and_out;
error = -EINVAL;
if (!S_ISREG(inode->i_mode))
goto dput_and_out;
error = mnt_want_write(path.mnt);
if (error)
goto dput_and_out;
error = inode_permission(inode, MAY_WRITE);
if (error)
goto mnt_drop_write_and_out;
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, FMODE_WRITE);
if (error)
goto put_write_and_out;
error = locks_verify_truncate(inode, NULL, length);
if (!error)
error = security_path_truncate(&path, length, 0);
if (!error) {
vfs_dq_init(inode);
error = do_truncate(path.dentry, length, 0, NULL);
}
put_write_and_out:
put_write_access(inode);
mnt_drop_write_and_out:
mnt_drop_write(path.mnt);
dput_and_out:
path_put(&path);
out:
return error;
}
SYSCALL_DEFINE2(truncate, const char __user *, path, unsigned long, length)
{
/* on 32-bit boxen it will cut the range 2^31--2^32-1 off */
return do_sys_truncate(path, (long)length);
}
static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
struct inode * inode;
struct dentry *dentry;
struct file * file;
int error;
error = -EINVAL;
if (length < 0)
goto out;
error = -EBADF;
file = fget(fd);
if (!file)
goto out;
/* 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;
error = -EINVAL;
if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
goto out_putf;
error = -EINVAL;
/* Cannot ftruncate over 2^31 bytes without large file support */
if (small && length > MAX_NON_LFS)
goto out_putf;
error = -EPERM;
if (IS_APPEND(inode))
goto out_putf;
error = locks_verify_truncate(inode, file, length);
if (!error)
error = security_path_truncate(&file->f_path, length,
ATTR_MTIME|ATTR_CTIME);
if (!error)
error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
out_putf:
fput(file);
out:
return error;
}
SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
{
long ret = do_sys_ftruncate(fd, length, 1);
/* avoid REGPARM breakage on x86: */
asmlinkage_protect(2, ret, fd, length);
return ret;
}
/* LFS versions of truncate are only needed on 32 bit machines */
#if BITS_PER_LONG == 32
SYSCALL_DEFINE(truncate64)(const char __user * path, loff_t length)
{
return do_sys_truncate(path, length);
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_truncate64(long path, loff_t length)
{
return SYSC_truncate64((const char __user *) path, length);
}
SYSCALL_ALIAS(sys_truncate64, SyS_truncate64);
#endif
SYSCALL_DEFINE(ftruncate64)(unsigned int fd, loff_t length)
{
long ret = do_sys_ftruncate(fd, length, 0);
/* avoid REGPARM breakage on x86: */
asmlinkage_protect(2, ret, fd, length);
return ret;
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_ftruncate64(long fd, loff_t length)
{
return SYSC_ftruncate64((unsigned int) fd, length);
}
SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
#endif
#endif /* BITS_PER_LONG == 32 */
int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
struct inode *inode = file->f_path.dentry->d_inode;
long ret;
if (offset < 0 || len <= 0)
return -EINVAL;
/* Return error if mode is not supported */
if (mode && !(mode & FALLOC_FL_KEEP_SIZE))
return -EOPNOTSUPP;
if (!(file->f_mode & FMODE_WRITE))
return -EBADF;
/*
* 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;
if (S_ISFIFO(inode->i_mode))
return -ESPIPE;
/*
* Let individual file system decide if it supports preallocation
* for directories or not.
*/
if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
return -ENODEV;
/* Check for wrap through zero too */
if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
return -EFBIG;
if (!inode->i_op->fallocate)
return -EOPNOTSUPP;
return inode->i_op->fallocate(inode, mode, offset, len);
}
SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)
{
struct file *file;
int error = -EBADF;
file = fget(fd);
if (file) {
error = do_fallocate(file, mode, offset, len);
fput(file);
}
return error;
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_fallocate(long fd, long mode, loff_t offset, loff_t len)
{
return SYSC_fallocate((int)fd, (int)mode, offset, len);
}
SYSCALL_ALIAS(sys_fallocate, SyS_fallocate);
#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.
*/
SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
{
const struct cred *old_cred;
struct cred *override_cred;
struct path path;
struct inode *inode;
int res;
if (mode & ~S_IRWXO) /* where's F_OK, X_OK, W_OK, R_OK? */
return -EINVAL;
override_cred = prepare_creds();
if (!override_cred)
return -ENOMEM;
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 */
if (override_cred->uid)
cap_clear(override_cred->cap_effective);
else
override_cred->cap_effective =
override_cred->cap_permitted;
}
old_cred = override_creds(override_cred);
res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
if (res)
goto out;
inode = path.dentry->d_inode;
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.mnt->mnt_flags & MNT_NOEXEC)
goto out_path_release;
}
res = inode_permission(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);
out:
revert_creds(old_cred);
put_cred(override_cred);
return res;
}
SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
{
return sys_faccessat(AT_FDCWD, filename, mode);
}
SYSCALL_DEFINE1(chdir, const char __user *, filename)
{
struct path path;
int error;
error = user_path_dir(filename, &path);
if (error)
goto out;
error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_ACCESS);
if (error)
goto dput_and_out;
set_fs_pwd(current->fs, &path);
dput_and_out:
path_put(&path);
out:
return error;
}
SYSCALL_DEFINE1(fchdir, unsigned int, fd)
{
struct file *file;
struct inode *inode;
int error;
error = -EBADF;
file = fget(fd);
if (!file)
goto out;
inode = file->f_path.dentry->d_inode;
error = -ENOTDIR;
if (!S_ISDIR(inode->i_mode))
goto out_putf;
error = inode_permission(inode, MAY_EXEC | MAY_ACCESS);
if (!error)
set_fs_pwd(current->fs, &file->f_path);
out_putf:
fput(file);
out:
return error;
}
SYSCALL_DEFINE1(chroot, const char __user *, filename)
{
struct path path;
int error;
error = user_path_dir(filename, &path);
if (error)
goto out;
error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_ACCESS);
if (error)
goto dput_and_out;
error = -EPERM;
if (!capable(CAP_SYS_CHROOT))
goto dput_and_out;
set_fs_root(current->fs, &path);
error = 0;
dput_and_out:
path_put(&path);
out:
return error;
}
SYSCALL_DEFINE2(fchmod, unsigned int, fd, mode_t, mode)
{
struct inode * inode;
struct dentry * dentry;
struct file * file;
int err = -EBADF;
struct iattr newattrs;
file = fget(fd);
if (!file)
goto out;
dentry = file->f_path.dentry;
inode = dentry->d_inode;
audit_inode(NULL, dentry);
err = mnt_want_write_file(file);
if (err)
goto out_putf;
mutex_lock(&inode->i_mutex);
if (mode == (mode_t) -1)
mode = inode->i_mode;
newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
err = notify_change(dentry, &newattrs);
mutex_unlock(&inode->i_mutex);
mnt_drop_write(file->f_path.mnt);
out_putf:
fput(file);
out:
return err;
}
SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, mode_t, mode)
{
struct path path;
struct inode *inode;
int error;
struct iattr newattrs;
error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
if (error)
goto out;
inode = path.dentry->d_inode;
error = mnt_want_write(path.mnt);
if (error)
goto dput_and_out;
mutex_lock(&inode->i_mutex);
if (mode == (mode_t) -1)
mode = inode->i_mode;
newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
error = notify_change(path.dentry, &newattrs);
mutex_unlock(&inode->i_mutex);
mnt_drop_write(path.mnt);
dput_and_out:
path_put(&path);
out:
return error;
}
SYSCALL_DEFINE2(chmod, const char __user *, filename, mode_t, mode)
{
return sys_fchmodat(AT_FDCWD, filename, mode);
}
static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
{
struct inode *inode = dentry->d_inode;
int error;
struct iattr newattrs;
newattrs.ia_valid = ATTR_CTIME;
if (user != (uid_t) -1) {
newattrs.ia_valid |= ATTR_UID;
newattrs.ia_uid = user;
}
if (group != (gid_t) -1) {
newattrs.ia_valid |= ATTR_GID;
newattrs.ia_gid = group;
}
if (!S_ISDIR(inode->i_mode))
newattrs.ia_valid |=
ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
mutex_lock(&inode->i_mutex);
error = notify_change(dentry, &newattrs);
mutex_unlock(&inode->i_mutex);
return error;
}
SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
{
struct path path;
int error;
error = user_path(filename, &path);
if (error)
goto out;
error = mnt_want_write(path.mnt);
if (error)
goto out_release;
error = chown_common(path.dentry, user, group);
mnt_drop_write(path.mnt);
out_release:
path_put(&path);
out:
return error;
}
SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
gid_t, group, int, flag)
{
struct path path;
int error = -EINVAL;
int follow;
if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0)
goto out;
follow = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
error = user_path_at(dfd, filename, follow, &path);
if (error)
goto out;
error = mnt_want_write(path.mnt);
if (error)
goto out_release;
error = chown_common(path.dentry, user, group);
mnt_drop_write(path.mnt);
out_release:
path_put(&path);
out:
return error;
}
SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
{
struct path path;
int error;
error = user_lpath(filename, &path);
if (error)
goto out;
error = mnt_want_write(path.mnt);
if (error)
goto out_release;
error = chown_common(path.dentry, user, group);
mnt_drop_write(path.mnt);
out_release:
path_put(&path);
out:
return error;
}
SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
{
struct file * file;
int error = -EBADF;
struct dentry * dentry;
file = fget(fd);
if (!file)
goto out;
error = mnt_want_write_file(file);
if (error)
goto out_fput;
dentry = file->f_path.dentry;
audit_inode(NULL, dentry);
error = chown_common(dentry, user, group);
mnt_drop_write(file->f_path.mnt);
out_fput:
fput(file);
out:
return error;
}
/*
* You have to be very careful that these write
* counts get cleaned up in error cases and
* upon __fput(). This should probably never
* be called outside of __dentry_open().
*/
static inline int __get_file_write_access(struct inode *inode,
struct vfsmount *mnt)
{
int error;
error = get_write_access(inode);
if (error)
return error;
/*
* Do not take mount writer counts on
* special files since no writes to
* the mount itself will occur.
*/
if (!special_file(inode->i_mode)) {
/*
* Balanced in __fput()
*/
error = mnt_want_write(mnt);
if (error)
put_write_access(inode);
}
return error;
}
static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
int flags, struct file *f,
int (*open)(struct inode *, struct file *),
const struct cred *cred)
{
struct inode *inode;
int error;
f->f_flags = flags;
f->f_mode = (__force fmode_t)((flags+1) & O_ACCMODE) | FMODE_LSEEK |
FMODE_PREAD | FMODE_PWRITE;
inode = dentry->d_inode;
if (f->f_mode & FMODE_WRITE) {
error = __get_file_write_access(inode, mnt);
if (error)
goto cleanup_file;
if (!special_file(inode->i_mode))
file_take_write(f);
}
f->f_mapping = inode->i_mapping;
f->f_path.dentry = dentry;
f->f_path.mnt = mnt;
f->f_pos = 0;
f->f_op = fops_get(inode->i_fop);
file_move(f, &inode->i_sb->s_files);
error = security_dentry_open(f, cred);
if (error)
goto cleanup_all;
if (!open && f->f_op)
open = f->f_op->open;
if (open) {
error = open(inode, f);
if (error)
goto cleanup_all;
}
f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
/* NB: we're sure to have correct a_ops only after f_op->open */
if (f->f_flags & O_DIRECT) {
if (!f->f_mapping->a_ops ||
((!f->f_mapping->a_ops->direct_IO) &&
(!f->f_mapping->a_ops->get_xip_mem))) {
fput(f);
f = ERR_PTR(-EINVAL);
}
}
return f;
cleanup_all:
fops_put(f->f_op);
if (f->f_mode & FMODE_WRITE) {
put_write_access(inode);
if (!special_file(inode->i_mode)) {
/*
* We don't consider this a real
* mnt_want/drop_write() pair
* because it all happenend right
* here, so just reset the state.
*/
file_reset_write(f);
mnt_drop_write(mnt);
}
}
file_kill(f);
f->f_path.dentry = NULL;
f->f_path.mnt = NULL;
cleanup_file:
put_filp(f);
dput(dentry);
mntput(mnt);
return ERR_PTR(error);
}
/**
* lookup_instantiate_filp - instantiates the open intent filp
* @nd: pointer to nameidata
* @dentry: pointer to dentry
* @open: open callback
*
* Helper for filesystems that want to use lookup open intents and pass back
* a fully instantiated struct file to the caller.
* This function is meant to be called from within a filesystem's
* lookup method.
* Beware of calling it for non-regular files! Those ->open methods might block
* (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
* leading to a deadlock, as nobody can open that fifo anymore, because
* another process to open fifo will block on locked parent when doing lookup).
* Note that in case of error, nd->intent.open.file is destroyed, but the
* path information remains valid.
* If the open callback is set to NULL, then the standard f_op->open()
* filesystem callback is substituted.
*/
struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
int (*open)(struct inode *, struct file *))
{
const struct cred *cred = current_cred();
if (IS_ERR(nd->intent.open.file))
goto out;
if (IS_ERR(dentry))
goto out_err;
nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
nd->intent.open.flags - 1,
nd->intent.open.file,
open, cred);
out:
return nd->intent.open.file;
out_err:
release_open_intent(nd);
nd->intent.open.file = (struct file *)dentry;
goto out;
}
EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
/**
* nameidata_to_filp - convert a nameidata to an open filp.
* @nd: pointer to nameidata
* @flags: open flags
*
* Note that this function destroys the original nameidata
*/
struct file *nameidata_to_filp(struct nameidata *nd, int flags)
{
const struct cred *cred = current_cred();
struct file *filp;
/* Pick up the filp from the open intent */
filp = nd->intent.open.file;
/* Has the filesystem initialised the file for us? */
if (filp->f_path.dentry == NULL)
filp = __dentry_open(nd->path.dentry, nd->path.mnt, flags, filp,
NULL, cred);
else
path_put(&nd->path);
return filp;
}
/*
* dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
* error.
*/
struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
const struct cred *cred)
{
int error;
struct file *f;
validate_creds(cred);
/*
* We must always pass in a valid mount pointer. Historically
* callers got away with not passing it, but we must enforce this at
* the earliest possible point now to avoid strange problems deep in the
* filesystem stack.
*/
if (!mnt) {
printk(KERN_WARNING "%s called with NULL vfsmount\n", __func__);
dump_stack();
return ERR_PTR(-EINVAL);
}
error = -ENFILE;
f = get_empty_filp();
if (f == NULL) {
dput(dentry);
mntput(mnt);
return ERR_PTR(error);
}
return __dentry_open(dentry, mnt, flags, f, NULL, cred);
}
EXPORT_SYMBOL(dentry_open);
static void __put_unused_fd(struct files_struct *files, unsigned int fd)
{
struct fdtable *fdt = files_fdtable(files);
__FD_CLR(fd, fdt->open_fds);
if (fd < files->next_fd)
files->next_fd = fd;
}
void put_unused_fd(unsigned int fd)
{
struct files_struct *files = current->files;
spin_lock(&files->file_lock);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);
}
EXPORT_SYMBOL(put_unused_fd);
/*
* Install a file pointer in the fd array.
*
* The VFS is full of places where we drop the files lock between
* setting the open_fds bitmap and installing the file in the file
* array. At any such point, we are vulnerable to a dup2() race
* installing a file in the array before us. We need to detect this and
* fput() the struct file we are about to overwrite in this case.
*
* It should never happen - if we allow dup2() do it, _really_ bad things
* will follow.
*/
void fd_install(unsigned int fd, struct file *file)
{
struct files_struct *files = current->files;
struct fdtable *fdt;
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
BUG_ON(fdt->fd[fd] != NULL);
rcu_assign_pointer(fdt->fd[fd], file);
spin_unlock(&files->file_lock);
}
EXPORT_SYMBOL(fd_install);
long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
{
char *tmp = getname(filename);
int fd = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
fd = get_unused_fd_flags(flags);
if (fd >= 0) {
struct file *f = do_filp_open(dfd, tmp, flags, mode, 0);
if (IS_ERR(f)) {
put_unused_fd(fd);
fd = PTR_ERR(f);
} else {
fsnotify_open(f->f_path.dentry);
fd_install(fd, f);
}
}
putname(tmp);
}
return fd;
}
SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, int, mode)
{
long ret;
if (force_o_largefile())
flags |= O_LARGEFILE;
ret = do_sys_open(AT_FDCWD, filename, flags, mode);
/* avoid REGPARM breakage on x86: */
asmlinkage_protect(3, ret, filename, flags, mode);
return ret;
}
SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
int, mode)
{
long ret;
if (force_o_largefile())
flags |= O_LARGEFILE;
ret = do_sys_open(dfd, filename, flags, mode);
/* avoid REGPARM breakage on x86: */
asmlinkage_protect(4, ret, dfd, filename, flags, mode);
return ret;
}
#ifndef __alpha__
/*
* For backward compatibility? Maybe this should be moved
* into arch/i386 instead?
*/
SYSCALL_DEFINE2(creat, const char __user *, pathname, int, mode)
{
return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
}
#endif
/*
* "id" is the POSIX thread ID. We use the
* files pointer for this..
*/
int filp_close(struct file *filp, fl_owner_t id)
{
int retval = 0;
if (!file_count(filp)) {
printk(KERN_ERR "VFS: Close: file count is 0\n");
return 0;
}
if (filp->f_op && filp->f_op->flush)
retval = filp->f_op->flush(filp, id);
dnotify_flush(filp, id);
locks_remove_posix(filp, id);
fput(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)
{
struct file * filp;
struct files_struct *files = current->files;
struct fdtable *fdt;
int retval;
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
if (fd >= fdt->max_fds)
goto out_unlock;
filp = fdt->fd[fd];
if (!filp)
goto out_unlock;
rcu_assign_pointer(fdt->fd[fd], NULL);
FD_CLR(fd, fdt->close_on_exec);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);
retval = filp_close(filp, files);
/* can't restart close syscall because file table entry was cleared */
if (unlikely(retval == -ERESTARTSYS ||
retval == -ERESTARTNOINTR ||
retval == -ERESTARTNOHAND ||
retval == -ERESTART_RESTARTBLOCK))
retval = -EINTR;
return retval;
out_unlock:
spin_unlock(&files->file_lock);
return -EBADF;
}
EXPORT_SYMBOL(sys_close);
/*
* 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
*/
int nonseekable_open(struct inode *inode, struct file *filp)
{
filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
return 0;
}
EXPORT_SYMBOL(nonseekable_open);