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Linux/security/apparmor/path.c

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  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/mount.h>
 17 #include <linux/namei.h>
 18 #include <linux/nsproxy.h>
 19 #include <linux/path.h>
 20 #include <linux/sched.h>
 21 #include <linux/slab.h>
 22 #include <linux/fs_struct.h>
 23 
 24 #include "include/apparmor.h"
 25 #include "include/path.h"
 26 #include "include/policy.h"
 27 
 28 /* modified from dcache.c */
 29 static int prepend(char **buffer, int buflen, const char *str, int namelen)
 30 {
 31         buflen -= namelen;
 32         if (buflen < 0)
 33                 return -ENAMETOOLONG;
 34         *buffer -= namelen;
 35         memcpy(*buffer, str, namelen);
 36         return 0;
 37 }
 38 
 39 #define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
 40 
 41 /* If the path is not connected to the expected root,
 42  * check if it is a sysctl and handle specially else remove any
 43  * leading / that __d_path may have returned.
 44  * Unless
 45  *     specifically directed to connect the path,
 46  * OR
 47  *     if in a chroot and doing chroot relative paths and the path
 48  *     resolves to the namespace root (would be connected outside
 49  *     of chroot) and specifically directed to connect paths to
 50  *     namespace root.
 51  */
 52 static int disconnect(const struct path *path, char *buf, char **name,
 53                       int flags, const char *disconnected)
 54 {
 55         int error = 0;
 56 
 57         if (!(flags & PATH_CONNECT_PATH) &&
 58             !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
 59               our_mnt(path->mnt))) {
 60                 /* disconnected path, don't return pathname starting
 61                  * with '/'
 62                  */
 63                 error = -EACCES;
 64                 if (**name == '/')
 65                         *name = *name + 1;
 66         } else {
 67                 if (**name != '/')
 68                         /* CONNECT_PATH with missing root */
 69                         error = prepend(name, *name - buf, "/", 1);
 70                 if (!error && disconnected)
 71                         error = prepend(name, *name - buf, disconnected,
 72                                         strlen(disconnected));
 73         }
 74 
 75         return error;
 76 }
 77 
 78 /**
 79  * d_namespace_path - lookup a name associated with a given path
 80  * @path: path to lookup  (NOT NULL)
 81  * @buf:  buffer to store path to  (NOT NULL)
 82  * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
 83  * @flags: flags controlling path lookup
 84  * @disconnected: string to prefix to disconnected paths
 85  *
 86  * Handle path name lookup.
 87  *
 88  * Returns: %0 else error code if path lookup fails
 89  *          When no error the path name is returned in @name which points to
 90  *          to a position in @buf
 91  */
 92 static int d_namespace_path(const struct path *path, char *buf, char **name,
 93                             int flags, const char *disconnected)
 94 {
 95         char *res;
 96         int error = 0;
 97         int connected = 1;
 98         int isdir = (flags & PATH_IS_DIR) ? 1 : 0;
 99         int buflen = aa_g_path_max - isdir;
100 
101         if (path->mnt->mnt_flags & MNT_INTERNAL) {
102                 /* it's not mounted anywhere */
103                 res = dentry_path(path->dentry, buf, buflen);
104                 *name = res;
105                 if (IS_ERR(res)) {
106                         *name = buf;
107                         return PTR_ERR(res);
108                 }
109                 if (path->dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
110                     strncmp(*name, "/sys/", 5) == 0) {
111                         /* TODO: convert over to using a per namespace
112                          * control instead of hard coded /proc
113                          */
114                         error = prepend(name, *name - buf, "/proc", 5);
115                         goto out;
116                 } else
117                         error = disconnect(path, buf, name, flags,
118                                            disconnected);
119                 goto out;
120         }
121 
122         /* resolve paths relative to chroot?*/
123         if (flags & PATH_CHROOT_REL) {
124                 struct path root;
125                 get_fs_root(current->fs, &root);
126                 res = __d_path(path, &root, buf, buflen);
127                 path_put(&root);
128         } else {
129                 res = d_absolute_path(path, buf, buflen);
130                 if (!our_mnt(path->mnt))
131                         connected = 0;
132         }
133 
134         /* handle error conditions - and still allow a partial path to
135          * be returned.
136          */
137         if (!res || IS_ERR(res)) {
138                 if (PTR_ERR(res) == -ENAMETOOLONG) {
139                         error = -ENAMETOOLONG;
140                         *name = buf;
141                         goto out;
142                 }
143                 connected = 0;
144                 res = dentry_path_raw(path->dentry, buf, buflen);
145                 if (IS_ERR(res)) {
146                         error = PTR_ERR(res);
147                         *name = buf;
148                         goto out;
149                 };
150         } else if (!our_mnt(path->mnt))
151                 connected = 0;
152 
153         *name = res;
154 
155         if (!connected)
156                 error = disconnect(path, buf, name, flags, disconnected);
157 
158         /* Handle two cases:
159          * 1. A deleted dentry && profile is not allowing mediation of deleted
160          * 2. On some filesystems, newly allocated dentries appear to the
161          *    security_path hooks as a deleted dentry except without an inode
162          *    allocated.
163          */
164         if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
165             !(flags & (PATH_MEDIATE_DELETED | PATH_DELEGATE_DELETED))) {
166                         error = -ENOENT;
167                         goto out;
168         }
169 
170 out:
171         /*
172          * Append "/" to the pathname.  The root directory is a special
173          * case; it already ends in slash.
174          */
175         if (!error && isdir && ((*name)[1] != '\0' || (*name)[0] != '/'))
176                 strcpy(&buf[aa_g_path_max - 2], "/");
177 
178         return error;
179 }
180 
181 /**
182  * aa_path_name - get the pathname to a buffer ensure dir / is appended
183  * @path: path the file  (NOT NULL)
184  * @flags: flags controlling path name generation
185  * @buffer: buffer to put name in (NOT NULL)
186  * @name: Returns - the generated path name if !error (NOT NULL)
187  * @info: Returns - information on why the path lookup failed (MAYBE NULL)
188  * @disconnected: string to prepend to disconnected paths
189  *
190  * @name is a pointer to the beginning of the pathname (which usually differs
191  * from the beginning of the buffer), or NULL.  If there is an error @name
192  * may contain a partial or invalid name that can be used for audit purposes,
193  * but it can not be used for mediation.
194  *
195  * We need PATH_IS_DIR to indicate whether the file is a directory or not
196  * because the file may not yet exist, and so we cannot check the inode's
197  * file type.
198  *
199  * Returns: %0 else error code if could retrieve name
200  */
201 int aa_path_name(const struct path *path, int flags, char *buffer,
202                  const char **name, const char **info, const char *disconnected)
203 {
204         char *str = NULL;
205         int error = d_namespace_path(path, buffer, &str, flags, disconnected);
206 
207         if (info && error) {
208                 if (error == -ENOENT)
209                         *info = "Failed name lookup - deleted entry";
210                 else if (error == -EACCES)
211                         *info = "Failed name lookup - disconnected path";
212                 else if (error == -ENAMETOOLONG)
213                         *info = "Failed name lookup - name too long";
214                 else
215                         *info = "Failed name lookup";
216         }
217 
218         *name = str;
219 
220         return error;
221 }
222 

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