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![James Morris](/assets/img/avatar_default.png)
This patch allows SELinux to canonicalize the value returned from getxattr() via the security_inode_getsecurity() hook, which is called after the fs level getxattr() function. The purpose of this is to allow the in-core security context for an inode to override the on-disk value. This could happen in cases such as upgrading a system to a different labeling form (e.g. standard SELinux to MLS) without needing to do a full relabel of the filesystem. In such cases, we want getxattr() to return the canonical security context that the kernel is using rather than what is stored on disk. The implementation hooks into the inode_getsecurity(), adding another parameter to indicate the result of the preceding fs-level getxattr() call, so that SELinux knows whether to compare a value obtained from disk with the kernel value. We also now allow getxattr() to work for mountpoint labeled filesystems (i.e. mount with option context=foo_t), as we are able to return the kernel value to the user. Signed-off-by: James Morris <jmorris@namei.org> Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
507 lines
11 KiB
C
507 lines
11 KiB
C
/*
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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 <asm/uaccess.h>
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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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down(&d->d_inode->i_sem);
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error = security_inode_setxattr(d, kname, kvalue, 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 (d->d_inode->i_op && d->d_inode->i_op->setxattr) {
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error = d->d_inode->i_op->setxattr(d, kname, kvalue,
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size, flags);
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if (!error) {
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fsnotify_xattr(d);
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security_inode_post_setxattr(d, kname, kvalue,
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size, flags);
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}
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} else if (!strncmp(kname, XATTR_SECURITY_PREFIX,
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sizeof XATTR_SECURITY_PREFIX - 1)) {
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const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1;
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error = security_inode_setsecurity(d->d_inode, suffix, kvalue,
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size, flags);
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if (!error)
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fsnotify_xattr(d);
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}
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out:
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up(&d->d_inode->i_sem);
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if (kvalue)
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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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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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error = setxattr(f->f_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 = security_inode_getxattr(d, kname);
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if (error)
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goto out;
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error = -EOPNOTSUPP;
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if (d->d_inode->i_op && d->d_inode->i_op->getxattr)
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error = d->d_inode->i_op->getxattr(d, kname, kvalue, size);
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if (!strncmp(kname, XATTR_SECURITY_PREFIX,
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sizeof XATTR_SECURITY_PREFIX - 1)) {
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const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1;
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int rv = security_inode_getsecurity(d->d_inode, suffix, kvalue,
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size, error);
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/* Security module active: overwrite error value */
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if (rv != -EOPNOTSUPP)
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error = rv;
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}
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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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out:
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if (kvalue)
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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_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 = security_inode_listxattr(d);
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if (error)
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goto out;
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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, klist, size);
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} else {
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error = security_inode_listsecurity(d->d_inode, klist, size);
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if (size && error >= size)
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error = -ERANGE;
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}
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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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out:
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if (klist)
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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_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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error = -EOPNOTSUPP;
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if (d->d_inode->i_op && d->d_inode->i_op->removexattr) {
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error = security_inode_removexattr(d, kname);
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if (error)
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goto out;
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down(&d->d_inode->i_sem);
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error = d->d_inode->i_op->removexattr(d, kname);
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up(&d->d_inode->i_sem);
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if (!error)
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fsnotify_xattr(d);
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}
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out:
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return error;
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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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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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error = removexattr(f->f_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)
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return -EOPNOTSUPP;
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return handler->get(inode, name, buffer, size);
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}
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/*
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* Combine the results of the list() operation from every xattr_handler in the
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* list.
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*/
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ssize_t
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generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
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{
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struct inode *inode = dentry->d_inode;
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struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr;
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unsigned int size = 0;
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if (!buffer) {
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for_each_xattr_handler(handlers, handler)
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size += handler->list(inode, NULL, 0, NULL, 0);
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} else {
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char *buf = buffer;
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for_each_xattr_handler(handlers, handler) {
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size = handler->list(inode, buf, buffer_size, NULL, 0);
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if (size > buffer_size)
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return -ERANGE;
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buf += size;
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buffer_size -= size;
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}
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size = buf - buffer;
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}
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return size;
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}
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/*
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* Find the handler for the prefix and dispatch its set() operation.
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*/
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int
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generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
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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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if (size == 0)
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value = ""; /* empty EA, do not remove */
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handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
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if (!handler)
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return -EOPNOTSUPP;
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return handler->set(inode, name, value, size, flags);
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}
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/*
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* Find the handler for the prefix and dispatch its set() operation to remove
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* any associated extended attribute.
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*/
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int
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generic_removexattr(struct dentry *dentry, const char *name)
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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)
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return -EOPNOTSUPP;
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return handler->set(inode, name, NULL, 0, XATTR_REPLACE);
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}
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EXPORT_SYMBOL(generic_getxattr);
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EXPORT_SYMBOL(generic_listxattr);
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EXPORT_SYMBOL(generic_setxattr);
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EXPORT_SYMBOL(generic_removexattr);
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