/*

File: fs/xattr.c

Extended attribute handling.

Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>

Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>

Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>

*/

#include <linux/fs.h>

#include <linux/slab.h>

#include <linux/file.h>

#include <linux/xattr.h>

#include <linux/mount.h>

#include <linux/namei.h>

#include <linux/security.h>

#include <linux/syscalls.h>

#include <linux/module.h>

#include <linux/fsnotify.h>

#include <linux/audit.h>

#include <asm/uaccess.h>

/*

* Check permissions for extended attribute access. This is a bit complicated

* because different namespaces have very different rules.

*/

static int

xattr_permission(struct inode *inode, const char *name, int mask)

{

/*

* We can never set or remove an extended attribute on a read-only

* filesystem or on an immutable / append-only inode.

*/

if (mask & MAY_WRITE) {

if (IS_IMMUTABLE(inode) || IS_APPEND(inode))

return -EPERM;

}

/*

* No restriction for security.* and system.* from the VFS. Decision

* on these is left to the underlying filesystem / security module.

*/

if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||

!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))

return 0;

/*

* The trusted.* namespace can only be accessed by a privileged user.

*/

if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))

return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);

/* In user.* namespace, only regular files and directories can have

* extended attributes. For sticky directories, only the owner and

* privileged user can write attributes.

*/

if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {

if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))

return -EPERM;

if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&

(mask & MAY_WRITE) && !is_owner_or_cap(inode))

return -EPERM;

}

return inode_permission(inode, mask);

}

int

vfs_setxattr(struct dentry *dentry, const char *name, const void *value,

size_t size, int flags)

{

struct inode *inode = dentry->d_inode;

int error;

error = xattr_permission(inode, name, MAY_WRITE);

if (error)

return error;

mutex_lock(&inode->i_mutex);

error = security_inode_setxattr(dentry, name, value, size, flags);

if (error)

goto out;

error = -EOPNOTSUPP;

if (inode->i_op->setxattr) {

error = inode->i_op->setxattr(dentry, name, value, size, flags);

if (!error) {

fsnotify_xattr(dentry);

security_inode_post_setxattr(dentry, name, value,

size, flags);

}

} else if (!strncmp(name, XATTR_SECURITY_PREFIX,

XATTR_SECURITY_PREFIX_LEN)) {

const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;

error = security_inode_setsecurity(inode, suffix, value,

size, flags);

if (!error)

fsnotify_xattr(dentry);

}

out:

mutex_unlock(&inode->i_mutex);

return error;

}

EXPORT_SYMBOL_GPL(vfs_setxattr);

ssize_t

xattr_getsecurity(struct inode *inode, const char *name, void *value,

size_t size)

{

void *buffer = NULL;

ssize_t len;

if (!value || !size) {

len = security_inode_getsecurity(inode, name, &buffer, false);

goto out_noalloc;

}

len = security_inode_getsecurity(inode, name, &buffer, true);

if (len < 0)

return len;

if (size < len) {

len = -ERANGE;

goto out;

}

memcpy(value, buffer, len);

out:

security_release_secctx(buffer, len);

out_noalloc:

return len;

}

EXPORT_SYMBOL_GPL(xattr_getsecurity);

ssize_t

vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)

{

struct inode *inode = dentry->d_inode;

int error;

error = xattr_permission(inode, name, MAY_READ);

if (error)

return error;

error = security_inode_getxattr(dentry, name);

if (error)

return error;

if (!strncmp(name, XATTR_SECURITY_PREFIX,

XATTR_SECURITY_PREFIX_LEN)) {

const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;

int ret = xattr_getsecurity(inode, suffix, value, size);

/*

* Only overwrite the return value if a security module

* is actually active.

*/

if (ret == -EOPNOTSUPP)

goto nolsm;

return ret;

}

nolsm:

if (inode->i_op->getxattr)

error = inode->i_op->getxattr(dentry, name, value, size);

else

error = -EOPNOTSUPP;

return error;

}

EXPORT_SYMBOL_GPL(vfs_getxattr);

ssize_t

vfs_listxattr(struct dentry *d, char *list, size_t size)

{

ssize_t error;

error = security_inode_listxattr(d);

if (error)

return error;

error = -EOPNOTSUPP;

if (d->d_inode->i_op->listxattr) {

error = d->d_inode->i_op->listxattr(d, list, size);

} else {

error = security_inode_listsecurity(d->d_inode, list, size);

if (size && error > size)

error = -ERANGE;

}

return error;

}

EXPORT_SYMBOL_GPL(vfs_listxattr);

int

vfs_removexattr(struct dentry *dentry, const char *name)

{

struct inode *inode = dentry->d_inode;

int error;

if (!inode->i_op->removexattr)

return -EOPNOTSUPP;

error = xattr_permission(inode, name, MAY_WRITE);

if (error)

return error;

error = security_inode_removexattr(dentry, name);

if (error)

return error;

mutex_lock(&inode->i_mutex);

error = inode->i_op->removexattr(dentry, name);

mutex_unlock(&inode->i_mutex);

if (!error)

fsnotify_xattr(dentry);

return error;

}

EXPORT_SYMBOL_GPL(vfs_removexattr);

/*

* Extended attribute SET operations

*/

static long

setxattr(struct dentry *d, const char __user *name, const void __user *value,

size_t size, int flags)

{

int error;

void *kvalue = NULL;

char kname[XATTR_NAME_MAX + 1];

if (flags & ~(XATTR_CREATE|XATTR_REPLACE))

return -EINVAL;

error = strncpy_from_user(kname, name, sizeof(kname));

if (error == 0 || error == sizeof(kname))

error = -ERANGE;

if (error < 0)

return error;

if (size) {

if (size > XATTR_SIZE_MAX)

return -E2BIG;

kvalue = kmalloc(size, GFP_KERNEL);

if (!kvalue)

return -ENOMEM;

if (copy_from_user(kvalue, value, size)) {

kfree(kvalue);

return -EFAULT;

}

}

error = vfs_setxattr(d, kname, kvalue, size, flags);

kfree(kvalue);

return error;

}

SYSCALL_DEFINE5(setxattr, const char __user *, pathname,

const char __user *, name, const void __user *, value,

size_t, size, int, flags)

{

struct path path;

int error;

error = user_path(pathname, &path);

if (error)

return error;

error = mnt_want_write(path.mnt);

if (!error) {

error = setxattr(path.dentry, name, value, size, flags);

mnt_drop_write(path.mnt);

}

path_put(&path);

return error;

}

SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,

const char __user *, name, const void __user *, value,

size_t, size, int, flags)

{

struct path path;

int error;

error = user_lpath(pathname, &path);

if (error)

return error;

error = mnt_want_write(path.mnt);

if (!error) {

error = setxattr(path.dentry, name, value, size, flags);

mnt_drop_write(path.mnt);

}

path_put(&path);

return error;

}

SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,

const void __user *,value, size_t, size, int, flags)

{

struct file *f;

struct dentry *dentry;

int error = -EBADF;

f = fget(fd);

if (!f)

return error;

dentry = f->f_path.dentry;

audit_inode(NULL, dentry);

error = mnt_want_write(f->f_path.mnt);

if (!error) {

error = setxattr(dentry, name, value, size, flags);

mnt_drop_write(f->f_path.mnt);

}

fput(f);

return error;

}

/*

* Extended attribute GET operations

*/

static ssize_t

getxattr(struct dentry *d, const char __user *name, void __user *value,

size_t size)

{

ssize_t error;

void *kvalue = NULL;

char kname[XATTR_NAME_MAX + 1];

error = strncpy_from_user(kname, name, sizeof(kname));

if (error == 0 || error == sizeof(kname))

error = -ERANGE;

if (error < 0)

return error;

if (size) {

if (size > XATTR_SIZE_MAX)

size = XATTR_SIZE_MAX;

kvalue = kzalloc(size, GFP_KERNEL);

if (!kvalue)

return -ENOMEM;

}

error = vfs_getxattr(d, kname, kvalue, size);

if (error > 0) {

if (size && copy_to_user(value, kvalue, error))

error = -EFAULT;

} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {

/* The file system tried to returned a value bigger

than XATTR_SIZE_MAX bytes. Not possible. */

error = -E2BIG;

}

kfree(kvalue);

return error;

}

SYSCALL_DEFINE4(getxattr, const char __user *, pathname,

const char __user *, name, void __user *, value, size_t, size)

{

struct path path;

ssize_t error;

error = user_path(pathname, &path);

if (error)

return error;

error = getxattr(path.dentry, name, value, size);

path_put(&path);

return error;

}

SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,

const char __user *, name, void __user *, value, size_t, size)

{

struct path path;

ssize_t error;

error = user_lpath(pathname, &path);

if (error)

return error;

error = getxattr(path.dentry, name, value, size);

path_put(&path);

return error;

}

SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,

void __user *, value, size_t, size)

{

struct file *f;

ssize_t error = -EBADF;

f = fget(fd);

if (!f)

return error;

audit_inode(NULL, f->f_path.dentry);

error = getxattr(f->f_path.dentry, name, value, size);

fput(f);

return error;

}

/*

* Extended attribute LIST operations

*/

static ssize_t

listxattr(struct dentry *d, char __user *list, size_t size)

{

ssize_t error;

char *klist = NULL;

if (size) {

if (size > XATTR_LIST_MAX)

size = XATTR_LIST_MAX;

klist = kmalloc(size, GFP_KERNEL);

if (!klist)

return -ENOMEM;

}

error = vfs_listxattr(d, klist, size);

if (error > 0) {

if (size && copy_to_user(list, klist, error))

error = -EFAULT;

} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {

/* The file system tried to returned a list bigger

than XATTR_LIST_MAX bytes. Not possible. */

error = -E2BIG;

}

kfree(klist);

return error;

}

SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,

size_t, size)

{

struct path path;

ssize_t error;

error = user_path(pathname, &path);

if (error)

return error;

error = listxattr(path.dentry, list, size);

path_put(&path);

return error;

}

SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,

size_t, size)

{

struct path path;

ssize_t error;

error = user_lpath(pathname, &path);

if (error)

return error;

error = listxattr(path.dentry, list, size);

path_put(&path);

return error;

}

SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)

{

struct file *f;

ssize_t error = -EBADF;

f = fget(fd);

if (!f)

return error;

audit_inode(NULL, f->f_path.dentry);

error = listxattr(f->f_path.dentry, list, size);

fput(f);

return error;

}

/*

* Extended attribute REMOVE operations

*/

static long

removexattr(struct dentry *d, const char __user *name)

{

int error;

char kname[XATTR_NAME_MAX + 1];

error = strncpy_from_user(kname, name, sizeof(kname));

if (error == 0 || error == sizeof(kname))

error = -ERANGE;

if (error < 0)

return error;

return vfs_removexattr(d, kname);

}

SYSCALL_DEFINE2(removexattr, const char __user *, pathname,

const char __user *, name)

{

struct path path;

int error;

error = user_path(pathname, &path);

if (error)

return error;

error = mnt_want_write(path.mnt);

if (!error) {

error = removexattr(path.dentry, name);

mnt_drop_write(path.mnt);

}

path_put(&path);

return error;

}

SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,

const char __user *, name)

{

struct path path;

int error;

error = user_lpath(pathname, &path);

if (error)

return error;

error = mnt_want_write(path.mnt);

if (!error) {

error = removexattr(path.dentry, name);

mnt_drop_write(path.mnt);

}

path_put(&path);

return error;

}

SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)

{

struct file *f;

struct dentry *dentry;

int error = -EBADF;

f = fget(fd);

if (!f)

return error;

dentry = f->f_path.dentry;

audit_inode(NULL, dentry);

error = mnt_want_write(f->f_path.mnt);

if (!error) {

error = removexattr(dentry, name);

mnt_drop_write(f->f_path.mnt);

}

fput(f);

return error;

}

static const char *

strcmp_prefix(const char *a, const char *a_prefix)

{

while (*a_prefix && *a == *a_prefix) {

a++;

a_prefix++;

}

return *a_prefix ? NULL : a;

}

/*

* In order to implement different sets of xattr operations for each xattr

* prefix with the generic xattr API, a filesystem should create a

* null-terminated array of struct xattr_handler (one for each prefix) and

* hang a pointer to it off of the s_xattr field of the superblock.

*

* The generic_fooxattr() functions will use this list to dispatch xattr

* operations to the correct xattr_handler.

*/

#define for_each_xattr_handler(handlers, handler) \

for ((handler) = *(handlers)++; \

(handler) != NULL; \

(handler) = *(handlers)++)

/*

* Find the xattr_handler with the matching prefix.

*/

static struct xattr_handler *

xattr_resolve_name(struct xattr_handler **handlers, const char **name)

{

struct xattr_handler *handler;

if (!*name)

return NULL;

for_each_xattr_handler(handlers, handler) {

const char *n = strcmp_prefix(*name, handler->prefix);

if (n) {

*name = n;

break;

}

}

return handler;

}

/*

* Find the handler for the prefix and dispatch its get() operation.

*/

ssize_t

generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)

{

struct xattr_handler *handler;

struct inode *inode = dentry->d_inode;

handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);

if (!handler)

return -EOPNOTSUPP;

return handler->get(inode, name, buffer, size);

}

/*

* Combine the results of the list() operation from every xattr_handler in the

* list.

*/

ssize_t

generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)

{

struct inode *inode = dentry->d_inode;

struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr;

unsigned int size = 0;

if (!buffer) {

for_each_xattr_handler(handlers, handler)

size += handler->list(inode, NULL, 0, NULL, 0);

} else {

char *buf = buffer;

for_each_xattr_handler(handlers, handler) {

size = handler->list(inode, buf, buffer_size, NULL, 0);

if (size > buffer_size)

return -ERANGE;

buf += size;

buffer_size -= size;

}

size = buf - buffer;

}

return size;

}

/*

* Find the handler for the prefix and dispatch its set() operation.

*/

int

generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)

{

struct xattr_handler *handler;

struct inode *inode = dentry->d_inode;

if (size == 0)

value = ""; /* empty EA, do not remove */

handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);

if (!handler)

return -EOPNOTSUPP;

return handler->set(inode, name, value, size, flags);

}

/*

* Find the handler for the prefix and dispatch its set() operation to remove

* any associated extended attribute.

*/

int

generic_removexattr(struct dentry *dentry, const char *name)

{

struct xattr_handler *handler;

struct inode *inode = dentry->d_inode;

handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);

if (!handler)

return -EOPNOTSUPP;

return handler->set(inode, name, NULL, 0, XATTR_REPLACE);

}

EXPORT_SYMBOL(generic_getxattr);

EXPORT_SYMBOL(generic_listxattr);

EXPORT_SYMBOL(generic_setxattr);

EXPORT_SYMBOL(generic_removexattr);