1 | /* Check if realpath does not consume extra stack space based on symlink |
2 | existance in the path (BZ #26341) |
3 | Copyright (C) 2021-2022 Free Software Foundation, Inc. |
4 | This file is part of the GNU C Library. |
5 | |
6 | The GNU C Library is free software; you can redistribute it and/or |
7 | modify it under the terms of the GNU Lesser General Public |
8 | License as published by the Free Software Foundation; either |
9 | version 2.1 of the License, or (at your option) any later version. |
10 | |
11 | The GNU C Library 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 GNU |
14 | Lesser General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU Lesser General Public |
17 | License along with the GNU C Library; if not, see |
18 | <https://www.gnu.org/licenses/>. */ |
19 | |
20 | #include <stdlib.h> |
21 | #include <string.h> |
22 | #include <sys/param.h> |
23 | #include <unistd.h> |
24 | |
25 | #define __sysconf sysconf |
26 | #include <eloop-threshold.h> |
27 | #include <support/check.h> |
28 | #include <support/support.h> |
29 | #include <support/temp_file.h> |
30 | #include <support/xunistd.h> |
31 | #include <support/xthread.h> |
32 | |
33 | static char *filename; |
34 | static size_t filenamelen; |
35 | static char *linkname; |
36 | |
37 | #ifndef PATH_MAX |
38 | # define PATH_MAX 1024 |
39 | #endif |
40 | |
41 | static void |
42 | create_link (void) |
43 | { |
44 | int fd = create_temp_file (base: "tst-canon-bz26341" , filename: &filename); |
45 | TEST_VERIFY_EXIT (fd != -1); |
46 | xclose (fd); |
47 | |
48 | /* Make filename a canonical path. */ |
49 | char *saved_filename = filename; |
50 | filename = realpath (name: filename, NULL); |
51 | free (ptr: saved_filename); |
52 | TEST_VERIFY (filename != NULL); |
53 | |
54 | /* Create MAXLINKS symbolic links to the temporary filename. |
55 | On exit, linkname has the last link created. */ |
56 | char *prevlink = filename; |
57 | int maxlinks = __eloop_threshold (); |
58 | for (int i = 0; i < maxlinks; i++) |
59 | { |
60 | linkname = xasprintf (format: "%s%d" , filename, i); |
61 | xsymlink (target: prevlink, linkpath: linkname); |
62 | add_temp_file (name: linkname); |
63 | prevlink = linkname; |
64 | } |
65 | |
66 | filenamelen = strlen (filename); |
67 | } |
68 | |
69 | static void * |
70 | do_realpath (void *arg) |
71 | { |
72 | /* Old implementation of realpath allocates a PATH_MAX using alloca |
73 | for each symlink in the path, leading to MAXSYMLINKS times PATH_MAX |
74 | maximum stack usage. |
75 | This stack allocations tries fill the thread allocated stack minus |
76 | the resolved path (plus some slack), the realpath (plus some |
77 | slack), and the system call usage (plus some slack). |
78 | If realpath uses more than 2 * PATH_MAX plus some slack it will trigger |
79 | a stackoverflow. */ |
80 | |
81 | const size_t syscall_usage = 1 * PATH_MAX + 1024; |
82 | const size_t realpath_usage = 2 * PATH_MAX + 1024; |
83 | const size_t thread_usage = 1 * PATH_MAX + 1024; |
84 | size_t stack_size = support_small_thread_stack_size () |
85 | - syscall_usage - realpath_usage - thread_usage; |
86 | char stack[stack_size]; |
87 | char *resolved = stack + stack_size - thread_usage + 1024; |
88 | |
89 | char *p = realpath (name: linkname, resolved: resolved); |
90 | TEST_VERIFY (p != NULL); |
91 | TEST_COMPARE_BLOB (resolved, filenamelen, filename, filenamelen); |
92 | |
93 | return NULL; |
94 | } |
95 | |
96 | static int |
97 | do_test (void) |
98 | { |
99 | create_link (); |
100 | |
101 | pthread_t th = xpthread_create (attr: support_small_stack_thread_attribute (), |
102 | thread_func: do_realpath, NULL); |
103 | xpthread_join (thr: th); |
104 | |
105 | return 0; |
106 | } |
107 | |
108 | #include <support/test-driver.c> |
109 | |