1 /* 2 * security/tomoyo/realpath.c 3 * 4 * Pathname calculation functions for TOMOYO. 5 * 6 * Copyright (C) 2005-2010 NTT DATA CORPORATION 7 */ 8 9 #include <linux/types.h> 10 #include <linux/mount.h> 11 #include <linux/mnt_namespace.h> 12 #include <linux/fs_struct.h> 13 #include <linux/magic.h> 14 #include <linux/slab.h> 15 #include <net/sock.h> 16 #include "common.h" 17 18 /** 19 * tomoyo_encode: Convert binary string to ascii string. 20 * 21 * @str: String in binary format. 22 * 23 * Returns pointer to @str in ascii format on success, NULL otherwise. 24 * 25 * This function uses kzalloc(), so caller must kfree() if this function 26 * didn't return NULL. 27 */ 28 char *tomoyo_encode(const char *str) 29 { 30 int len = 0; 31 const char *p = str; 32 char *cp; 33 char *cp0; 34 35 if (!p) 36 return NULL; 37 while (*p) { 38 const unsigned char c = *p++; 39 if (c == '\\') 40 len += 2; 41 else if (c > ' ' && c < 127) 42 len++; 43 else 44 len += 4; 45 } 46 len++; 47 /* Reserve space for appending "/". */ 48 cp = kzalloc(len + 10, GFP_NOFS); 49 if (!cp) 50 return NULL; 51 cp0 = cp; 52 p = str; 53 while (*p) { 54 const unsigned char c = *p++; 55 56 if (c == '\\') { 57 *cp++ = '\\'; 58 *cp++ = '\\'; 59 } else if (c > ' ' && c < 127) { 60 *cp++ = c; 61 } else { 62 *cp++ = '\\'; 63 *cp++ = (c >> 6) + '0'; 64 *cp++ = ((c >> 3) & 7) + '0'; 65 *cp++ = (c & 7) + '0'; 66 } 67 } 68 return cp0; 69 } 70 71 /** 72 * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root. 73 * 74 * @path: Pointer to "struct path". 75 * 76 * Returns the realpath of the given @path on success, NULL otherwise. 77 * 78 * If dentry is a directory, trailing '/' is appended. 79 * Characters out of 0x20 < c < 0x7F range are converted to 80 * \ooo style octal string. 81 * Character \ is converted to \\ string. 82 * 83 * These functions use kzalloc(), so the caller must call kfree() 84 * if these functions didn't return NULL. 85 */ 86 char *tomoyo_realpath_from_path(struct path *path) 87 { 88 char *buf = NULL; 89 char *name = NULL; 90 unsigned int buf_len = PAGE_SIZE / 2; 91 struct dentry *dentry = path->dentry; 92 bool is_dir; 93 if (!dentry) 94 return NULL; 95 is_dir = dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode); 96 while (1) { 97 struct path ns_root = { .mnt = NULL, .dentry = NULL }; 98 char *pos; 99 buf_len <<= 1; 100 kfree(buf); 101 buf = kmalloc(buf_len, GFP_NOFS); 102 if (!buf) 103 break; 104 /* Get better name for socket. */ 105 if (dentry->d_sb && dentry->d_sb->s_magic == SOCKFS_MAGIC) { 106 struct inode *inode = dentry->d_inode; 107 struct socket *sock = inode ? SOCKET_I(inode) : NULL; 108 struct sock *sk = sock ? sock->sk : NULL; 109 if (sk) { 110 snprintf(buf, buf_len - 1, "socket:[family=%u:" 111 "type=%u:protocol=%u]", sk->sk_family, 112 sk->sk_type, sk->sk_protocol); 113 } else { 114 snprintf(buf, buf_len - 1, "socket:[unknown]"); 115 } 116 name = tomoyo_encode(buf); 117 break; 118 } 119 /* For "socket:[\$]" and "pipe:[\$]". */ 120 if (dentry->d_op && dentry->d_op->d_dname) { 121 pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1); 122 if (IS_ERR(pos)) 123 continue; 124 name = tomoyo_encode(pos); 125 break; 126 } 127 /* If we don't have a vfsmount, we can't calculate. */ 128 if (!path->mnt) 129 break; 130 /* go to whatever namespace root we are under */ 131 pos = __d_path(path, &ns_root, buf, buf_len); 132 /* Prepend "/proc" prefix if using internal proc vfs mount. */ 133 if (!IS_ERR(pos) && (path->mnt->mnt_flags & MNT_INTERNAL) && 134 (path->mnt->mnt_sb->s_magic == PROC_SUPER_MAGIC)) { 135 pos -= 5; 136 if (pos >= buf) 137 memcpy(pos, "/proc", 5); 138 else 139 pos = ERR_PTR(-ENOMEM); 140 } 141 if (IS_ERR(pos)) 142 continue; 143 name = tomoyo_encode(pos); 144 break; 145 } 146 kfree(buf); 147 if (!name) 148 tomoyo_warn_oom(__func__); 149 else if (is_dir && *name) { 150 /* Append trailing '/' if dentry is a directory. */ 151 char *pos = name + strlen(name) - 1; 152 if (*pos != '/') 153 /* 154 * This is OK because tomoyo_encode() reserves space 155 * for appending "/". 156 */ 157 *++pos = '/'; 158 } 159 return name; 160 } 161 162 /** 163 * tomoyo_realpath_nofollow - Get realpath of a pathname. 164 * 165 * @pathname: The pathname to solve. 166 * 167 * Returns the realpath of @pathname on success, NULL otherwise. 168 */ 169 char *tomoyo_realpath_nofollow(const char *pathname) 170 { 171 struct path path; 172 173 if (pathname && kern_path(pathname, 0, &path) == 0) { 174 char *buf = tomoyo_realpath_from_path(&path); 175 path_put(&path); 176 return buf; 177 } 178 return NULL; 179 } 180