Commit | Line | Data |
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09c434b8 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
1da177e4 LT |
2 | /* |
3 | * linux/fs/binfmt_script.c | |
4 | * | |
96de0e25 | 5 | * Copyright (C) 1996 Martin von Löwis |
1da177e4 LT |
6 | * original #!-checking implemented by tytso. |
7 | */ | |
8 | ||
9 | #include <linux/module.h> | |
10 | #include <linux/string.h> | |
11 | #include <linux/stat.h> | |
1da177e4 LT |
12 | #include <linux/binfmts.h> |
13 | #include <linux/init.h> | |
14 | #include <linux/file.h> | |
1da177e4 LT |
15 | #include <linux/err.h> |
16 | #include <linux/fs.h> | |
17 | ||
b5372fe5 | 18 | static inline bool spacetab(char c) { return c == ' ' || c == '\t'; } |
ccbb18b6 | 19 | static inline const char *next_non_spacetab(const char *first, const char *last) |
b5372fe5 KC |
20 | { |
21 | for (; first <= last; first++) | |
22 | if (!spacetab(*first)) | |
23 | return first; | |
24 | return NULL; | |
25 | } | |
ccbb18b6 | 26 | static inline const char *next_terminator(const char *first, const char *last) |
b5372fe5 KC |
27 | { |
28 | for (; first <= last; first++) | |
29 | if (spacetab(*first) || !*first) | |
30 | return first; | |
31 | return NULL; | |
32 | } | |
33 | ||
71613c3b | 34 | static int load_script(struct linux_binprm *bprm) |
1da177e4 | 35 | { |
ccbb18b6 | 36 | const char *i_name, *i_sep, *i_arg, *i_end, *buf_end; |
1da177e4 | 37 | struct file *file; |
1da177e4 LT |
38 | int retval; |
39 | ||
b5372fe5 | 40 | /* Not ours to exec if we don't start with "#!". */ |
d7402698 | 41 | if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!')) |
1da177e4 | 42 | return -ENOEXEC; |
51f39a1f | 43 | |
b5372fe5 KC |
44 | /* |
45 | * This section handles parsing the #! line into separate | |
46 | * interpreter path and argument strings. We must be careful | |
47 | * because bprm->buf is not yet guaranteed to be NUL-terminated | |
48 | * (though the buffer will have trailing NUL padding when the | |
49 | * file size was smaller than the buffer size). | |
50 | * | |
51 | * We do not want to exec a truncated interpreter path, so either | |
52 | * we find a newline (which indicates nothing is truncated), or | |
53 | * we find a space/tab/NUL after the interpreter path (which | |
54 | * itself may be preceded by spaces/tabs). Truncating the | |
55 | * arguments is fine: the interpreter can re-read the script to | |
56 | * parse them on its own. | |
57 | */ | |
58 | buf_end = bprm->buf + sizeof(bprm->buf) - 1; | |
ccbb18b6 EB |
59 | i_end = strnchr(bprm->buf, sizeof(bprm->buf), '\n'); |
60 | if (!i_end) { | |
61 | i_end = next_non_spacetab(bprm->buf + 2, buf_end); | |
62 | if (!i_end) | |
b5372fe5 KC |
63 | return -ENOEXEC; /* Entire buf is spaces/tabs */ |
64 | /* | |
65 | * If there is no later space/tab/NUL we must assume the | |
66 | * interpreter path is truncated. | |
67 | */ | |
ccbb18b6 | 68 | if (!next_terminator(i_end, buf_end)) |
b5372fe5 | 69 | return -ENOEXEC; |
ccbb18b6 | 70 | i_end = buf_end; |
b5372fe5 | 71 | } |
ccbb18b6 EB |
72 | /* Trim any trailing spaces/tabs from i_end */ |
73 | while (spacetab(i_end[-1])) | |
74 | i_end--; | |
75 | ||
76 | /* Skip over leading spaces/tabs */ | |
77 | i_name = next_non_spacetab(bprm->buf+2, i_end); | |
78 | if (!i_name || (i_name == i_end)) | |
1da177e4 | 79 | return -ENOEXEC; /* No interpreter name found */ |
ccbb18b6 EB |
80 | |
81 | /* Is there an optional argument? */ | |
1da177e4 | 82 | i_arg = NULL; |
ccbb18b6 EB |
83 | i_sep = next_terminator(i_name, i_end); |
84 | if (i_sep && (*i_sep != '\0')) | |
85 | i_arg = next_non_spacetab(i_sep, i_end); | |
86 | ||
87 | /* | |
88 | * If the script filename will be inaccessible after exec, typically | |
89 | * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give | |
90 | * up now (on the assumption that the interpreter will want to load | |
91 | * this file). | |
92 | */ | |
93 | if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE) | |
94 | return -ENOENT; | |
95 | ||
1da177e4 LT |
96 | /* |
97 | * OK, we've parsed out the interpreter name and | |
98 | * (optional) argument. | |
99 | * Splice in (1) the interpreter's name for argv[0] | |
100 | * (2) (optional) argument to interpreter | |
101 | * (3) filename of shell script (replace argv[0]) | |
102 | * | |
103 | * This is done in reverse order, because of how the | |
104 | * user environment and arguments are stored. | |
105 | */ | |
b6a2fea3 OW |
106 | retval = remove_arg_zero(bprm); |
107 | if (retval) | |
108 | return retval; | |
986db2d1 | 109 | retval = copy_string_kernel(bprm->interp, bprm); |
c2315c18 ON |
110 | if (retval < 0) |
111 | return retval; | |
1da177e4 | 112 | bprm->argc++; |
ccbb18b6 | 113 | *((char *)i_end) = '\0'; |
1da177e4 | 114 | if (i_arg) { |
ccbb18b6 | 115 | *((char *)i_sep) = '\0'; |
986db2d1 | 116 | retval = copy_string_kernel(i_arg, bprm); |
c2315c18 ON |
117 | if (retval < 0) |
118 | return retval; | |
1da177e4 LT |
119 | bprm->argc++; |
120 | } | |
986db2d1 | 121 | retval = copy_string_kernel(i_name, bprm); |
c2315c18 ON |
122 | if (retval) |
123 | return retval; | |
1da177e4 | 124 | bprm->argc++; |
c2315c18 | 125 | retval = bprm_change_interp(i_name, bprm); |
b66c5984 KC |
126 | if (retval < 0) |
127 | return retval; | |
1da177e4 LT |
128 | |
129 | /* | |
130 | * OK, now restart the process with the interpreter's dentry. | |
131 | */ | |
c2315c18 | 132 | file = open_exec(i_name); |
1da177e4 LT |
133 | if (IS_ERR(file)) |
134 | return PTR_ERR(file); | |
135 | ||
bc2bf338 EB |
136 | bprm->interpreter = file; |
137 | return 0; | |
1da177e4 LT |
138 | } |
139 | ||
140 | static struct linux_binfmt script_format = { | |
141 | .module = THIS_MODULE, | |
142 | .load_binary = load_script, | |
143 | }; | |
144 | ||
145 | static int __init init_script_binfmt(void) | |
146 | { | |
8fc3dc5a AV |
147 | register_binfmt(&script_format); |
148 | return 0; | |
1da177e4 LT |
149 | } |
150 | ||
151 | static void __exit exit_script_binfmt(void) | |
152 | { | |
153 | unregister_binfmt(&script_format); | |
154 | } | |
155 | ||
156 | core_initcall(init_script_binfmt); | |
157 | module_exit(exit_script_binfmt); | |
158 | MODULE_LICENSE("GPL"); |