1 /* 2 * AppArmor security module 3 * 4 * This file contains AppArmor function for pathnames 5 * 6 * Copyright (C) 1998-2008 Novell/SUSE 7 * Copyright 2009-2010 Canonical Ltd. 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License as 11 * published by the Free Software Foundation, version 2 of the 12 * License. 13 */ 14 15 #include <linux/magic.h> 16 #include <linux/mnt_namespace.h> 17 #include <linux/mount.h> 18 #include <linux/namei.h> 19 #include <linux/nsproxy.h> 20 #include <linux/path.h> 21 #include <linux/sched.h> 22 #include <linux/slab.h> 23 #include <linux/fs_struct.h> 24 25 #include "include/apparmor.h" 26 #include "include/path.h" 27 #include "include/policy.h" 28 29 30 /* modified from dcache.c */ 31 static int prepend(char **buffer, int buflen, const char *str, int namelen) 32 { 33 buflen -= namelen; 34 if (buflen < 0) 35 return -ENAMETOOLONG; 36 *buffer -= namelen; 37 memcpy(*buffer, str, namelen); 38 return 0; 39 } 40 41 #define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT) 42 43 /** 44 * d_namespace_path - lookup a name associated with a given path 45 * @path: path to lookup (NOT NULL) 46 * @buf: buffer to store path to (NOT NULL) 47 * @buflen: length of @buf 48 * @name: Returns - pointer for start of path name with in @buf (NOT NULL) 49 * @flags: flags controlling path lookup 50 * 51 * Handle path name lookup. 52 * 53 * Returns: %0 else error code if path lookup fails 54 * When no error the path name is returned in @name which points to 55 * to a position in @buf 56 */ 57 static int d_namespace_path(struct path *path, char *buf, int buflen, 58 char **name, int flags) 59 { 60 struct path root, tmp; 61 char *res; 62 int deleted, connected; 63 int error = 0; 64 65 /* Get the root we want to resolve too, released below */ 66 if (flags & PATH_CHROOT_REL) { 67 /* resolve paths relative to chroot */ 68 get_fs_root(current->fs, &root); 69 } else { 70 /* resolve paths relative to namespace */ 71 root.mnt = current->nsproxy->mnt_ns->root; 72 root.dentry = root.mnt->mnt_root; 73 path_get(&root); 74 } 75 76 spin_lock(&dcache_lock); 77 /* There is a race window between path lookup here and the 78 * need to strip the " (deleted) string that __d_path applies 79 * Detect the race and relookup the path 80 * 81 * The stripping of (deleted) is a hack that could be removed 82 * with an updated __d_path 83 */ 84 do { 85 tmp = root; 86 deleted = d_unlinked(path->dentry); 87 res = __d_path(path, &tmp, buf, buflen); 88 89 } while (deleted != d_unlinked(path->dentry)); 90 spin_unlock(&dcache_lock); 91 92 *name = res; 93 /* handle error conditions - and still allow a partial path to 94 * be returned. 95 */ 96 if (IS_ERR(res)) { 97 error = PTR_ERR(res); 98 *name = buf; 99 goto out; 100 } 101 if (deleted) { 102 /* On some filesystems, newly allocated dentries appear to the 103 * security_path hooks as a deleted dentry except without an 104 * inode allocated. 105 * 106 * Remove the appended deleted text and return as string for 107 * normal mediation, or auditing. The (deleted) string is 108 * guaranteed to be added in this case, so just strip it. 109 */ 110 buf[buflen - 11] = 0; /* - (len(" (deleted)") +\0) */ 111 112 if (path->dentry->d_inode && !(flags & PATH_MEDIATE_DELETED)) { 113 error = -ENOENT; 114 goto out; 115 } 116 } 117 118 /* Determine if the path is connected to the expected root */ 119 connected = tmp.dentry == root.dentry && tmp.mnt == root.mnt; 120 121 /* If the path is not connected, 122 * check if it is a sysctl and handle specially else remove any 123 * leading / that __d_path may have returned. 124 * Unless 125 * specifically directed to connect the path, 126 * OR 127 * if in a chroot and doing chroot relative paths and the path 128 * resolves to the namespace root (would be connected outside 129 * of chroot) and specifically directed to connect paths to 130 * namespace root. 131 */ 132 if (!connected) { 133 /* is the disconnect path a sysctl? */ 134 if (tmp.dentry->d_sb->s_magic == PROC_SUPER_MAGIC && 135 strncmp(*name, "/sys/", 5) == 0) { 136 /* TODO: convert over to using a per namespace 137 * control instead of hard coded /proc 138 */ 139 error = prepend(name, *name - buf, "/proc", 5); 140 } else if (!(flags & PATH_CONNECT_PATH) && 141 !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) && 142 (tmp.mnt == current->nsproxy->mnt_ns->root && 143 tmp.dentry == tmp.mnt->mnt_root))) { 144 /* disconnected path, don't return pathname starting 145 * with '/' 146 */ 147 error = -ESTALE; 148 if (*res == '/') 149 *name = res + 1; 150 } 151 } 152 153 out: 154 path_put(&root); 155 156 return error; 157 } 158 159 /** 160 * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended 161 * @path: path to get name for (NOT NULL) 162 * @flags: flags controlling path lookup 163 * @buffer: buffer to put name in (NOT NULL) 164 * @size: size of buffer 165 * @name: Returns - contains position of path name in @buffer (NOT NULL) 166 * 167 * Returns: %0 else error on failure 168 */ 169 static int get_name_to_buffer(struct path *path, int flags, char *buffer, 170 int size, char **name) 171 { 172 int adjust = (flags & PATH_IS_DIR) ? 1 : 0; 173 int error = d_namespace_path(path, buffer, size - adjust, name, flags); 174 175 if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0') 176 /* 177 * Append "/" to the pathname. The root directory is a special 178 * case; it already ends in slash. 179 */ 180 strcpy(&buffer[size - 2], "/"); 181 182 return error; 183 } 184 185 /** 186 * aa_get_name - compute the pathname of a file 187 * @path: path the file (NOT NULL) 188 * @flags: flags controlling path name generation 189 * @buffer: buffer that aa_get_name() allocated (NOT NULL) 190 * @name: Returns - the generated path name if !error (NOT NULL) 191 * 192 * @name is a pointer to the beginning of the pathname (which usually differs 193 * from the beginning of the buffer), or NULL. If there is an error @name 194 * may contain a partial or invalid name that can be used for audit purposes, 195 * but it can not be used for mediation. 196 * 197 * We need PATH_IS_DIR to indicate whether the file is a directory or not 198 * because the file may not yet exist, and so we cannot check the inode's 199 * file type. 200 * 201 * Returns: %0 else error code if could retrieve name 202 */ 203 int aa_get_name(struct path *path, int flags, char **buffer, const char **name) 204 { 205 char *buf, *str = NULL; 206 int size = 256; 207 int error; 208 209 *name = NULL; 210 *buffer = NULL; 211 for (;;) { 212 /* freed by caller */ 213 buf = kmalloc(size, GFP_KERNEL); 214 if (!buf) 215 return -ENOMEM; 216 217 error = get_name_to_buffer(path, flags, buf, size, &str); 218 if (error != -ENAMETOOLONG) 219 break; 220 221 kfree(buf); 222 size <<= 1; 223 if (size > aa_g_path_max) 224 return -ENAMETOOLONG; 225 } 226 *buffer = buf; 227 *name = str; 228 229 return error; 230 } 231