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linux-next/fs/xattr.c
akpm@osdl.org e0ad7b073e [PATCH] move xattr permission checks into the VFS
)

From: Christoph Hellwig <hch@lst.de>

The xattr code has rather complex permission checks because the rules are very
different for different attribute namespaces.  This patch moves as much as we
can into the generic code.  Currently all the major disk based filesystems
duplicate these checks, while many minor filesystems or network filesystems
lack some or all of them.

To do this we need defines for the extended attribute names in common code, I
moved them up from JFS which had the nicest defintions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 08:01:29 -08:00

598 lines
13 KiB
C

/*
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/smp_lock.h>
#include <linux/file.h>
#include <linux/xattr.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/module.h>
#include <linux/fsnotify.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_RDONLY(inode))
return -EROFS;
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 accessed by a privilegued user.
*/
if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
if (!S_ISREG(inode->i_mode) &&
(!S_ISDIR(inode->i_mode) || inode->i_mode & S_ISVTX))
return -EPERM;
}
return permission(inode, mask, NULL);
}
int
vfs_setxattr(struct dentry *dentry, char *name, 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
vfs_getxattr(struct dentry *dentry, 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 (inode->i_op->getxattr)
error = inode->i_op->getxattr(dentry, name, value, size);
else
error = -EOPNOTSUPP;
if (!strncmp(name, XATTR_SECURITY_PREFIX,
XATTR_SECURITY_PREFIX_LEN)) {
const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
int ret = security_inode_getsecurity(inode, suffix, value,
size, error);
/*
* Only overwrite the return value if a security module
* is actually active.
*/
if (ret != -EOPNOTSUPP)
error = ret;
}
return error;
}
EXPORT_SYMBOL_GPL(vfs_getxattr);
int
vfs_removexattr(struct dentry *dentry, 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, char __user *name, 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(char __user *path, char __user *name, void __user *value,
size_t size, int flags)
{
struct nameidata nd;
int error;
error = user_path_walk(path, &nd);
if (error)
return error;
error = setxattr(nd.dentry, name, value, size, flags);
path_release(&nd);
return error;
}
asmlinkage long
sys_lsetxattr(char __user *path, char __user *name, void __user *value,
size_t size, int flags)
{
struct nameidata nd;
int error;
error = user_path_walk_link(path, &nd);
if (error)
return error;
error = setxattr(nd.dentry, name, value, size, flags);
path_release(&nd);
return error;
}
asmlinkage long
sys_fsetxattr(int fd, char __user *name, void __user *value,
size_t size, int flags)
{
struct file *f;
int error = -EBADF;
f = fget(fd);
if (!f)
return error;
error = setxattr(f->f_dentry, name, value, size, flags);
fput(f);
return error;
}
/*
* Extended attribute GET operations
*/
static ssize_t
getxattr(struct dentry *d, 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(char __user *path, char __user *name, void __user *value,
size_t size)
{
struct nameidata nd;
ssize_t error;
error = user_path_walk(path, &nd);
if (error)
return error;
error = getxattr(nd.dentry, name, value, size);
path_release(&nd);
return error;
}
asmlinkage ssize_t
sys_lgetxattr(char __user *path, char __user *name, void __user *value,
size_t size)
{
struct nameidata nd;
ssize_t error;
error = user_path_walk_link(path, &nd);
if (error)
return error;
error = getxattr(nd.dentry, name, value, size);
path_release(&nd);
return error;
}
asmlinkage ssize_t
sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size)
{
struct file *f;
ssize_t error = -EBADF;
f = fget(fd);
if (!f)
return error;
error = getxattr(f->f_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 = security_inode_listxattr(d);
if (error)
goto out;
error = -EOPNOTSUPP;
if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {
error = d->d_inode->i_op->listxattr(d, klist, size);
} else {
error = security_inode_listsecurity(d->d_inode, klist, size);
if (size && error > size)
error = -ERANGE;
}
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;
}
out:
kfree(klist);
return error;
}
asmlinkage ssize_t
sys_listxattr(char __user *path, char __user *list, size_t size)
{
struct nameidata nd;
ssize_t error;
error = user_path_walk(path, &nd);
if (error)
return error;
error = listxattr(nd.dentry, list, size);
path_release(&nd);
return error;
}
asmlinkage ssize_t
sys_llistxattr(char __user *path, char __user *list, size_t size)
{
struct nameidata nd;
ssize_t error;
error = user_path_walk_link(path, &nd);
if (error)
return error;
error = listxattr(nd.dentry, list, size);
path_release(&nd);
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;
error = listxattr(f->f_dentry, list, size);
fput(f);
return error;
}
/*
* Extended attribute REMOVE operations
*/
static long
removexattr(struct dentry *d, 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(char __user *path, char __user *name)
{
struct nameidata nd;
int error;
error = user_path_walk(path, &nd);
if (error)
return error;
error = removexattr(nd.dentry, name);
path_release(&nd);
return error;
}
asmlinkage long
sys_lremovexattr(char __user *path, char __user *name)
{
struct nameidata nd;
int error;
error = user_path_walk_link(path, &nd);
if (error)
return error;
error = removexattr(nd.dentry, name);
path_release(&nd);
return error;
}
asmlinkage long
sys_fremovexattr(int fd, char __user *name)
{
struct file *f;
int error = -EBADF;
f = fget(fd);
if (!f)
return error;
error = removexattr(f->f_dentry, name);
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);