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authorJohn Johansen <john.johansen@canonical.com>2010-07-29 14:47:57 -0700
committerJames Morris <jmorris@namei.org>2010-08-02 15:35:11 +1000
commitcdff264264254e0fabc8107a33f3bb75a95e981f (patch)
treea20956e2a7a38e195071ded57fca02e1d1b1314c /security/apparmor/path.c
parente6f6a4cc955d626ed26562d98de5766bf1f73526 (diff)
AppArmor: misc. base functions and defines
Miscellaneous functions and defines needed by AppArmor, including the base path resolution routines. Signed-off-by: John Johansen <john.johansen@canonical.com> Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'security/apparmor/path.c')
-rw-r--r--security/apparmor/path.c235
1 files changed, 235 insertions, 0 deletions
diff --git a/security/apparmor/path.c b/security/apparmor/path.c
new file mode 100644
index 000000000000..96bab9469d48
--- /dev/null
+++ b/security/apparmor/path.c
@@ -0,0 +1,235 @@
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor function for pathnames
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ */
+
+#include <linux/magic.h>
+#include <linux/mnt_namespace.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/nsproxy.h>
+#include <linux/path.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/fs_struct.h>
+
+#include "include/apparmor.h"
+#include "include/path.h"
+#include "include/policy.h"
+
+
+/* modified from dcache.c */
+static int prepend(char **buffer, int buflen, const char *str, int namelen)
+{
+ buflen -= namelen;
+ if (buflen < 0)
+ return -ENAMETOOLONG;
+ *buffer -= namelen;
+ memcpy(*buffer, str, namelen);
+ return 0;
+}
+
+#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
+
+/**
+ * d_namespace_path - lookup a name associated with a given path
+ * @path: path to lookup (NOT NULL)
+ * @buf: buffer to store path to (NOT NULL)
+ * @buflen: length of @buf
+ * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
+ * @flags: flags controlling path lookup
+ *
+ * Handle path name lookup.
+ *
+ * Returns: %0 else error code if path lookup fails
+ * When no error the path name is returned in @name which points to
+ * to a position in @buf
+ */
+static int d_namespace_path(struct path *path, char *buf, int buflen,
+ char **name, int flags)
+{
+ struct path root, tmp;
+ char *res;
+ int deleted, connected;
+ int error = 0;
+
+ /* Get the root we want to resolve too */
+ if (flags & PATH_CHROOT_REL) {
+ /* resolve paths relative to chroot */
+ read_lock(&current->fs->lock);
+ root = current->fs->root;
+ /* released below */
+ path_get(&root);
+ read_unlock(&current->fs->lock);
+ } else {
+ /* resolve paths relative to namespace */
+ root.mnt = current->nsproxy->mnt_ns->root;
+ root.dentry = root.mnt->mnt_root;
+ /* released below */
+ path_get(&root);
+ }
+
+ spin_lock(&dcache_lock);
+ /* There is a race window between path lookup here and the
+ * need to strip the " (deleted) string that __d_path applies
+ * Detect the race and relookup the path
+ *
+ * The stripping of (deleted) is a hack that could be removed
+ * with an updated __d_path
+ */
+ do {
+ tmp = root;
+ deleted = d_unlinked(path->dentry);
+ res = __d_path(path, &tmp, buf, buflen);
+
+ } while (deleted != d_unlinked(path->dentry));
+ spin_unlock(&dcache_lock);
+
+ *name = res;
+ /* handle error conditions - and still allow a partial path to
+ * be returned.
+ */
+ if (IS_ERR(res)) {
+ error = PTR_ERR(res);
+ *name = buf;
+ goto out;
+ }
+ if (deleted) {
+ /* On some filesystems, newly allocated dentries appear to the
+ * security_path hooks as a deleted dentry except without an
+ * inode allocated.
+ *
+ * Remove the appended deleted text and return as string for
+ * normal mediation, or auditing. The (deleted) string is
+ * guaranteed to be added in this case, so just strip it.
+ */
+ buf[buflen - 11] = 0; /* - (len(" (deleted)") +\0) */
+
+ if (path->dentry->d_inode && !(flags & PATH_MEDIATE_DELETED)) {
+ error = -ENOENT;
+ goto out;
+ }
+ }
+
+ /* Determine if the path is connected to the expected root */
+ connected = tmp.dentry == root.dentry && tmp.mnt == root.mnt;
+
+ /* If the path is not connected,
+ * check if it is a sysctl and handle specially else remove any
+ * leading / that __d_path may have returned.
+ * Unless
+ * specifically directed to connect the path,
+ * OR
+ * if in a chroot and doing chroot relative paths and the path
+ * resolves to the namespace root (would be connected outside
+ * of chroot) and specifically directed to connect paths to
+ * namespace root.
+ */
+ if (!connected) {
+ /* is the disconnect path a sysctl? */
+ if (tmp.dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
+ strncmp(*name, "/sys/", 5) == 0) {
+ /* TODO: convert over to using a per namespace
+ * control instead of hard coded /proc
+ */
+ error = prepend(name, *name - buf, "/proc", 5);
+ } else if (!(flags & PATH_CONNECT_PATH) &&
+ !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
+ (tmp.mnt == current->nsproxy->mnt_ns->root &&
+ tmp.dentry == tmp.mnt->mnt_root))) {
+ /* disconnected path, don't return pathname starting
+ * with '/'
+ */
+ error = -ESTALE;
+ if (*res == '/')
+ *name = res + 1;
+ }
+ }
+
+out:
+ path_put(&root);
+
+ return error;
+}
+
+/**
+ * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
+ * @path: path to get name for (NOT NULL)
+ * @flags: flags controlling path lookup
+ * @buffer: buffer to put name in (NOT NULL)
+ * @size: size of buffer
+ * @name: Returns - contains position of path name in @buffer (NOT NULL)
+ *
+ * Returns: %0 else error on failure
+ */
+static int get_name_to_buffer(struct path *path, int flags, char *buffer,
+ int size, char **name)
+{
+ int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
+ int error = d_namespace_path(path, buffer, size - adjust, name, flags);
+
+ if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
+ /*
+ * Append "/" to the pathname. The root directory is a special
+ * case; it already ends in slash.
+ */
+ strcpy(&buffer[size - 2], "/");
+
+ return error;
+}
+
+/**
+ * aa_get_name - compute the pathname of a file
+ * @path: path the file (NOT NULL)
+ * @flags: flags controlling path name generation
+ * @buffer: buffer that aa_get_name() allocated (NOT NULL)
+ * @name: Returns - the generated path name if !error (NOT NULL)
+ *
+ * @name is a pointer to the beginning of the pathname (which usually differs
+ * from the beginning of the buffer), or NULL. If there is an error @name
+ * may contain a partial or invalid name that can be used for audit purposes,
+ * but it can not be used for mediation.
+ *
+ * We need PATH_IS_DIR to indicate whether the file is a directory or not
+ * because the file may not yet exist, and so we cannot check the inode's
+ * file type.
+ *
+ * Returns: %0 else error code if could retrieve name
+ */
+int aa_get_name(struct path *path, int flags, char **buffer, const char **name)
+{
+ char *buf, *str = NULL;
+ int size = 256;
+ int error;
+
+ *name = NULL;
+ *buffer = NULL;
+ for (;;) {
+ /* freed by caller */
+ buf = kmalloc(size, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ error = get_name_to_buffer(path, flags, buf, size, &str);
+ if (error != -ENAMETOOLONG)
+ break;
+
+ kfree(buf);
+ size <<= 1;
+ if (size > aa_g_path_max)
+ return -ENAMETOOLONG;
+ }
+ *buffer = buf;
+ *name = str;
+
+ return error;
+}

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