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DEFINITIONS
This source file includes following definitions.
- xattr_permission
- vfs_setxattr
- xattr_getsecurity
- vfs_getxattr
- vfs_listxattr
- vfs_removexattr
- setxattr
- sys_setxattr
- sys_lsetxattr
- sys_fsetxattr
- getxattr
- sys_getxattr
- sys_lgetxattr
- sys_fgetxattr
- listxattr
- sys_listxattr
- sys_llistxattr
- sys_flistxattr
- removexattr
- sys_removexattr
- sys_lremovexattr
- sys_fremovexattr
- strcmp_prefix
- xattr_resolve_name
- generic_getxattr
- generic_listxattr
- generic_setxattr
- generic_removexattr
/*
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 && 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;
}
asmlinkage long
sys_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;
}
asmlinkage long
sys_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;
}
asmlinkage long
sys_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;
}
asmlinkage ssize_t
sys_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;
}
asmlinkage ssize_t
sys_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;
}
asmlinkage ssize_t
sys_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;
}
asmlinkage ssize_t
sys_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;
}
asmlinkage ssize_t
sys_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;
}
asmlinkage ssize_t
sys_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);
}
asmlinkage long
sys_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;
}
asmlinkage long
sys_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;
}
asmlinkage long
sys_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);