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620 lines
14 KiB
620 lines
14 KiB
/*
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File: fs/xattr.c
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Extended attribute handling.
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Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
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Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
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Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
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*/
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/smp_lock.h>
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#include <linux/file.h>
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#include <linux/xattr.h>
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#include <linux/namei.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/module.h>
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#include <linux/fsnotify.h>
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#include <linux/audit.h>
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#include <asm/uaccess.h>
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/*
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* Check permissions for extended attribute access. This is a bit complicated
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* because different namespaces have very different rules.
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*/
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static int
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xattr_permission(struct inode *inode, const char *name, int mask)
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{
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/*
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* We can never set or remove an extended attribute on a read-only
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* filesystem or on an immutable / append-only inode.
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*/
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if (mask & MAY_WRITE) {
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if (IS_RDONLY(inode))
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return -EROFS;
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if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
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return -EPERM;
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}
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/*
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* No restriction for security.* and system.* from the VFS. Decision
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* on these is left to the underlying filesystem / security module.
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*/
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if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
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!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
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return 0;
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/*
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* The trusted.* namespace can only be accessed by a privileged user.
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*/
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if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
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return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
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/* In user.* namespace, only regular files and directories can have
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* extended attributes. For sticky directories, only the owner and
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* privileged user can write attributes.
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*/
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if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
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if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
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return -EPERM;
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if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
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(mask & MAY_WRITE) && (current->fsuid != inode->i_uid) &&
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!capable(CAP_FOWNER))
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return -EPERM;
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}
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return permission(inode, mask, NULL);
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}
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int
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vfs_setxattr(struct dentry *dentry, char *name, void *value,
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size_t size, int flags)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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error = xattr_permission(inode, name, MAY_WRITE);
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if (error)
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return error;
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mutex_lock(&inode->i_mutex);
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error = security_inode_setxattr(dentry, name, value, size, flags);
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if (error)
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goto out;
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error = -EOPNOTSUPP;
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if (inode->i_op->setxattr) {
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error = inode->i_op->setxattr(dentry, name, value, size, flags);
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if (!error) {
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fsnotify_xattr(dentry);
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security_inode_post_setxattr(dentry, name, value,
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size, flags);
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}
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} else if (!strncmp(name, XATTR_SECURITY_PREFIX,
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XATTR_SECURITY_PREFIX_LEN)) {
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const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
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error = security_inode_setsecurity(inode, suffix, value,
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size, flags);
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if (!error)
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fsnotify_xattr(dentry);
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}
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out:
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mutex_unlock(&inode->i_mutex);
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return error;
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}
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EXPORT_SYMBOL_GPL(vfs_setxattr);
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ssize_t
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vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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error = xattr_permission(inode, name, MAY_READ);
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if (error)
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return error;
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error = security_inode_getxattr(dentry, name);
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if (error)
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return error;
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if (inode->i_op->getxattr)
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error = inode->i_op->getxattr(dentry, name, value, size);
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else
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error = -EOPNOTSUPP;
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if (!strncmp(name, XATTR_SECURITY_PREFIX,
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XATTR_SECURITY_PREFIX_LEN)) {
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const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
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int ret = security_inode_getsecurity(inode, suffix, value,
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size, error);
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/*
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* Only overwrite the return value if a security module
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* is actually active.
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*/
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if (ret != -EOPNOTSUPP)
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error = ret;
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}
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return error;
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}
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EXPORT_SYMBOL_GPL(vfs_getxattr);
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ssize_t
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vfs_listxattr(struct dentry *d, char *list, size_t size)
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{
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ssize_t error;
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error = security_inode_listxattr(d);
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if (error)
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return error;
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error = -EOPNOTSUPP;
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if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {
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error = d->d_inode->i_op->listxattr(d, list, size);
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} else {
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error = security_inode_listsecurity(d->d_inode, list, size);
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if (size && error > size)
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error = -ERANGE;
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}
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return error;
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}
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EXPORT_SYMBOL_GPL(vfs_listxattr);
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int
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vfs_removexattr(struct dentry *dentry, char *name)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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if (!inode->i_op->removexattr)
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return -EOPNOTSUPP;
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error = xattr_permission(inode, name, MAY_WRITE);
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if (error)
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return error;
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error = security_inode_removexattr(dentry, name);
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if (error)
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return error;
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mutex_lock(&inode->i_mutex);
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error = inode->i_op->removexattr(dentry, name);
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mutex_unlock(&inode->i_mutex);
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if (!error)
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fsnotify_xattr(dentry);
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return error;
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}
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EXPORT_SYMBOL_GPL(vfs_removexattr);
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/*
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* Extended attribute SET operations
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*/
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static long
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setxattr(struct dentry *d, char __user *name, void __user *value,
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size_t size, int flags)
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{
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int error;
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void *kvalue = NULL;
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char kname[XATTR_NAME_MAX + 1];
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if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
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return -EINVAL;
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error = strncpy_from_user(kname, name, sizeof(kname));
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if (error == 0 || error == sizeof(kname))
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error = -ERANGE;
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if (error < 0)
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return error;
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if (size) {
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if (size > XATTR_SIZE_MAX)
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return -E2BIG;
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kvalue = kmalloc(size, GFP_KERNEL);
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if (!kvalue)
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return -ENOMEM;
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if (copy_from_user(kvalue, value, size)) {
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kfree(kvalue);
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return -EFAULT;
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}
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}
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error = vfs_setxattr(d, kname, kvalue, size, flags);
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kfree(kvalue);
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return error;
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}
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asmlinkage long
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sys_setxattr(char __user *path, char __user *name, void __user *value,
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size_t size, int flags)
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{
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struct nameidata nd;
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int error;
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error = user_path_walk(path, &nd);
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if (error)
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return error;
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error = setxattr(nd.dentry, name, value, size, flags);
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path_release(&nd);
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return error;
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}
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asmlinkage long
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sys_lsetxattr(char __user *path, char __user *name, void __user *value,
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size_t size, int flags)
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{
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struct nameidata nd;
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int error;
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error = user_path_walk_link(path, &nd);
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if (error)
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return error;
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error = setxattr(nd.dentry, name, value, size, flags);
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path_release(&nd);
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return error;
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}
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asmlinkage long
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sys_fsetxattr(int fd, char __user *name, void __user *value,
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size_t size, int flags)
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{
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struct file *f;
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struct dentry *dentry;
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int error = -EBADF;
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f = fget(fd);
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if (!f)
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return error;
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dentry = f->f_path.dentry;
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audit_inode(NULL, dentry->d_inode);
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error = setxattr(dentry, name, value, size, flags);
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fput(f);
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return error;
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}
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/*
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* Extended attribute GET operations
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*/
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static ssize_t
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getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
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{
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ssize_t error;
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void *kvalue = NULL;
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char kname[XATTR_NAME_MAX + 1];
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error = strncpy_from_user(kname, name, sizeof(kname));
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if (error == 0 || error == sizeof(kname))
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error = -ERANGE;
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if (error < 0)
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return error;
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if (size) {
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if (size > XATTR_SIZE_MAX)
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size = XATTR_SIZE_MAX;
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kvalue = kzalloc(size, GFP_KERNEL);
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if (!kvalue)
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return -ENOMEM;
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}
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error = vfs_getxattr(d, kname, kvalue, size);
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if (error > 0) {
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if (size && copy_to_user(value, kvalue, error))
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error = -EFAULT;
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} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
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/* The file system tried to returned a value bigger
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than XATTR_SIZE_MAX bytes. Not possible. */
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error = -E2BIG;
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}
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kfree(kvalue);
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return error;
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}
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asmlinkage ssize_t
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sys_getxattr(char __user *path, char __user *name, void __user *value,
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size_t size)
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{
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struct nameidata nd;
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ssize_t error;
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error = user_path_walk(path, &nd);
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if (error)
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return error;
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error = getxattr(nd.dentry, name, value, size);
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path_release(&nd);
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return error;
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}
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asmlinkage ssize_t
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sys_lgetxattr(char __user *path, char __user *name, void __user *value,
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size_t size)
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{
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struct nameidata nd;
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ssize_t error;
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error = user_path_walk_link(path, &nd);
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if (error)
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return error;
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error = getxattr(nd.dentry, name, value, size);
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path_release(&nd);
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return error;
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}
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asmlinkage ssize_t
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sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size)
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{
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struct file *f;
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ssize_t error = -EBADF;
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f = fget(fd);
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if (!f)
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return error;
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error = getxattr(f->f_path.dentry, name, value, size);
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fput(f);
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return error;
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}
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/*
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* Extended attribute LIST operations
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*/
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static ssize_t
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listxattr(struct dentry *d, char __user *list, size_t size)
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{
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ssize_t error;
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char *klist = NULL;
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if (size) {
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if (size > XATTR_LIST_MAX)
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size = XATTR_LIST_MAX;
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klist = kmalloc(size, GFP_KERNEL);
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if (!klist)
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return -ENOMEM;
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}
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error = vfs_listxattr(d, klist, size);
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if (error > 0) {
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if (size && copy_to_user(list, klist, error))
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error = -EFAULT;
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} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
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/* The file system tried to returned a list bigger
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than XATTR_LIST_MAX bytes. Not possible. */
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error = -E2BIG;
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}
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kfree(klist);
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return error;
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}
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asmlinkage ssize_t
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sys_listxattr(char __user *path, char __user *list, size_t size)
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{
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struct nameidata nd;
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ssize_t error;
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error = user_path_walk(path, &nd);
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if (error)
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return error;
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error = listxattr(nd.dentry, list, size);
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path_release(&nd);
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return error;
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}
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asmlinkage ssize_t
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sys_llistxattr(char __user *path, char __user *list, size_t size)
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{
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struct nameidata nd;
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ssize_t error;
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error = user_path_walk_link(path, &nd);
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if (error)
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return error;
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error = listxattr(nd.dentry, list, size);
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path_release(&nd);
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return error;
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}
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asmlinkage ssize_t
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sys_flistxattr(int fd, char __user *list, size_t size)
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{
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struct file *f;
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ssize_t error = -EBADF;
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f = fget(fd);
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if (!f)
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return error;
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error = listxattr(f->f_path.dentry, list, size);
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fput(f);
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return error;
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}
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/*
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* Extended attribute REMOVE operations
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*/
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static long
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removexattr(struct dentry *d, char __user *name)
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{
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int error;
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char kname[XATTR_NAME_MAX + 1];
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error = strncpy_from_user(kname, name, sizeof(kname));
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if (error == 0 || error == sizeof(kname))
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error = -ERANGE;
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if (error < 0)
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return error;
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return vfs_removexattr(d, kname);
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}
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asmlinkage long
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sys_removexattr(char __user *path, char __user *name)
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{
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struct nameidata nd;
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int error;
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error = user_path_walk(path, &nd);
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if (error)
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return error;
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error = removexattr(nd.dentry, name);
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path_release(&nd);
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return error;
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}
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asmlinkage long
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sys_lremovexattr(char __user *path, char __user *name)
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{
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struct nameidata nd;
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int error;
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error = user_path_walk_link(path, &nd);
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if (error)
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return error;
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error = removexattr(nd.dentry, name);
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path_release(&nd);
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return error;
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}
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asmlinkage long
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sys_fremovexattr(int fd, char __user *name)
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{
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struct file *f;
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struct dentry *dentry;
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int error = -EBADF;
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f = fget(fd);
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if (!f)
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return error;
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dentry = f->f_path.dentry;
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audit_inode(NULL, dentry->d_inode);
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error = removexattr(dentry, name);
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fput(f);
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return error;
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}
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static const char *
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strcmp_prefix(const char *a, const char *a_prefix)
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{
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while (*a_prefix && *a == *a_prefix) {
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a++;
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a_prefix++;
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}
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return *a_prefix ? NULL : a;
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}
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/*
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* In order to implement different sets of xattr operations for each xattr
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* prefix with the generic xattr API, a filesystem should create a
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* null-terminated array of struct xattr_handler (one for each prefix) and
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* hang a pointer to it off of the s_xattr field of the superblock.
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*
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* The generic_fooxattr() functions will use this list to dispatch xattr
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* operations to the correct xattr_handler.
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*/
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#define for_each_xattr_handler(handlers, handler) \
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for ((handler) = *(handlers)++; \
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(handler) != NULL; \
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(handler) = *(handlers)++)
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/*
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* Find the xattr_handler with the matching prefix.
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*/
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static struct xattr_handler *
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xattr_resolve_name(struct xattr_handler **handlers, const char **name)
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{
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struct xattr_handler *handler;
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if (!*name)
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return NULL;
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for_each_xattr_handler(handlers, handler) {
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const char *n = strcmp_prefix(*name, handler->prefix);
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if (n) {
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*name = n;
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break;
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}
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}
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return handler;
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}
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/*
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* Find the handler for the prefix and dispatch its get() operation.
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*/
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ssize_t
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generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
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{
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struct xattr_handler *handler;
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struct inode *inode = dentry->d_inode;
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handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
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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);
|
|
|