Fix handling of missing syscall in Linux mkdirat.
[glibc.git] / elf / chroot_canon.c
blob54a6a4cc96b4e3d2351a8fba8aea7fef19fec7a1
1 /* Return the canonical absolute name of a given file inside chroot.
2 Copyright (C) 1996,1997,1998,1999,2000,2001,2004,2005,2010
3 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published
8 by the Free Software Foundation; version 2 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software Foundation,
18 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
20 #include <stdlib.h>
21 #include <string.h>
22 #include <unistd.h>
23 #include <limits.h>
24 #include <sys/param.h>
25 #include <sys/stat.h>
26 #include <errno.h>
27 #include <stddef.h>
28 #include <stdint.h>
30 #include <ldconfig.h>
32 #ifndef PATH_MAX
33 #define PATH_MAX 1024
34 #endif
36 /* Return the canonical absolute name of file NAME as if chroot(CHROOT) was
37 done first. A canonical name does not contain any `.', `..' components
38 nor any repeated path separators ('/') or symlinks. All path components
39 must exist and NAME must be absolute filename. The result is malloc'd.
40 The returned name includes the CHROOT prefix. */
42 char *
43 chroot_canon (const char *chroot, const char *name)
45 char *rpath;
46 char *dest;
47 char *extra_buf = NULL;
48 char *rpath_root;
49 const char *start;
50 const char *end;
51 const char *rpath_limit;
52 int num_links = 0;
53 size_t chroot_len = strlen (chroot);
55 if (chroot_len < 1)
57 __set_errno (EINVAL);
58 return NULL;
61 rpath = xmalloc (chroot_len + PATH_MAX);
63 rpath_limit = rpath + chroot_len + PATH_MAX;
65 rpath_root = (char *) mempcpy (rpath, chroot, chroot_len) - 1;
66 if (*rpath_root != '/')
67 *++rpath_root = '/';
68 dest = rpath_root + 1;
70 for (start = end = name; *start; start = end)
72 struct stat64 st;
73 int n;
75 /* Skip sequence of multiple path-separators. */
76 while (*start == '/')
77 ++start;
79 /* Find end of path component. */
80 for (end = start; *end && *end != '/'; ++end)
81 /* Nothing. */;
83 if (end - start == 0)
84 break;
85 else if (end - start == 1 && start[0] == '.')
86 /* nothing */;
87 else if (end - start == 2 && start[0] == '.' && start[1] == '.')
89 /* Back up to previous component, ignore if at root already. */
90 if (dest > rpath_root + 1)
91 while ((--dest)[-1] != '/');
93 else
95 size_t new_size;
97 if (dest[-1] != '/')
98 *dest++ = '/';
100 if (dest + (end - start) >= rpath_limit)
102 ptrdiff_t dest_offset = dest - rpath;
103 char *new_rpath;
105 new_size = rpath_limit - rpath;
106 if (end - start + 1 > PATH_MAX)
107 new_size += end - start + 1;
108 else
109 new_size += PATH_MAX;
110 new_rpath = (char *) xrealloc (rpath, new_size);
111 rpath = new_rpath;
112 rpath_limit = rpath + new_size;
114 dest = rpath + dest_offset;
117 dest = mempcpy (dest, start, end - start);
118 *dest = '\0';
120 if (lstat64 (rpath, &st) < 0)
122 if (*end == '\0')
123 goto done;
124 goto error;
127 if (S_ISLNK (st.st_mode))
129 char *buf = alloca (PATH_MAX);
130 size_t len;
132 if (++num_links > MAXSYMLINKS)
134 __set_errno (ELOOP);
135 goto error;
138 n = readlink (rpath, buf, PATH_MAX);
139 if (n < 0)
141 if (*end == '\0')
142 goto done;
143 goto error;
145 buf[n] = '\0';
147 if (!extra_buf)
148 extra_buf = alloca (PATH_MAX);
150 len = strlen (end);
151 if ((long int) (n + len) >= PATH_MAX)
153 __set_errno (ENAMETOOLONG);
154 goto error;
157 /* Careful here, end may be a pointer into extra_buf... */
158 memmove (&extra_buf[n], end, len + 1);
159 name = end = memcpy (extra_buf, buf, n);
161 if (buf[0] == '/')
162 dest = rpath_root + 1; /* It's an absolute symlink */
163 else
164 /* Back up to previous component, ignore if at root already: */
165 if (dest > rpath_root + 1)
166 while ((--dest)[-1] != '/');
170 done:
171 if (dest > rpath_root + 1 && dest[-1] == '/')
172 --dest;
173 *dest = '\0';
175 return rpath;
177 error:
178 free (rpath);
179 return NULL;