diff options
Diffstat (limited to 'fs/binfmt_script.c')
| -rw-r--r-- | fs/binfmt_script.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c new file mode 100644 index 000000000..1b6625e95 --- /dev/null +++ b/fs/binfmt_script.c @@ -0,0 +1,158 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/fs/binfmt_script.c + * + * Copyright (C) 1996 Martin von Löwis + * original #!-checking implemented by tytso. + */ + +#include <linux/module.h> +#include <linux/string.h> +#include <linux/stat.h> +#include <linux/binfmts.h> +#include <linux/init.h> +#include <linux/file.h> +#include <linux/err.h> +#include <linux/fs.h> + +static inline bool spacetab(char c) { return c == ' ' || c == '\t'; } +static inline const char *next_non_spacetab(const char *first, const char *last) +{ + for (; first <= last; first++) + if (!spacetab(*first)) + return first; + return NULL; +} +static inline const char *next_terminator(const char *first, const char *last) +{ + for (; first <= last; first++) + if (spacetab(*first) || !*first) + return first; + return NULL; +} + +static int load_script(struct linux_binprm *bprm) +{ + const char *i_name, *i_sep, *i_arg, *i_end, *buf_end; + struct file *file; + int retval; + + /* Not ours to exec if we don't start with "#!". */ + if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!')) + return -ENOEXEC; + + /* + * This section handles parsing the #! line into separate + * interpreter path and argument strings. We must be careful + * because bprm->buf is not yet guaranteed to be NUL-terminated + * (though the buffer will have trailing NUL padding when the + * file size was smaller than the buffer size). + * + * We do not want to exec a truncated interpreter path, so either + * we find a newline (which indicates nothing is truncated), or + * we find a space/tab/NUL after the interpreter path (which + * itself may be preceded by spaces/tabs). Truncating the + * arguments is fine: the interpreter can re-read the script to + * parse them on its own. + */ + buf_end = bprm->buf + sizeof(bprm->buf) - 1; + i_end = strnchr(bprm->buf, sizeof(bprm->buf), '\n'); + if (!i_end) { + i_end = next_non_spacetab(bprm->buf + 2, buf_end); + if (!i_end) + return -ENOEXEC; /* Entire buf is spaces/tabs */ + /* + * If there is no later space/tab/NUL we must assume the + * interpreter path is truncated. + */ + if (!next_terminator(i_end, buf_end)) + return -ENOEXEC; + i_end = buf_end; + } + /* Trim any trailing spaces/tabs from i_end */ + while (spacetab(i_end[-1])) + i_end--; + + /* Skip over leading spaces/tabs */ + i_name = next_non_spacetab(bprm->buf+2, i_end); + if (!i_name || (i_name == i_end)) + return -ENOEXEC; /* No interpreter name found */ + + /* Is there an optional argument? */ + i_arg = NULL; + i_sep = next_terminator(i_name, i_end); + if (i_sep && (*i_sep != '\0')) + i_arg = next_non_spacetab(i_sep, i_end); + + /* + * If the script filename will be inaccessible after exec, typically + * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give + * up now (on the assumption that the interpreter will want to load + * this file). + */ + if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE) + return -ENOENT; + + /* + * OK, we've parsed out the interpreter name and + * (optional) argument. + * Splice in (1) the interpreter's name for argv[0] + * (2) (optional) argument to interpreter + * (3) filename of shell script (replace argv[0]) + * + * This is done in reverse order, because of how the + * user environment and arguments are stored. + */ + retval = remove_arg_zero(bprm); + if (retval) + return retval; + retval = copy_string_kernel(bprm->interp, bprm); + if (retval < 0) + return retval; + bprm->argc++; + *((char *)i_end) = '\0'; + if (i_arg) { + *((char *)i_sep) = '\0'; + retval = copy_string_kernel(i_arg, bprm); + if (retval < 0) + return retval; + bprm->argc++; + } + retval = copy_string_kernel(i_name, bprm); + if (retval) + return retval; + bprm->argc++; + retval = bprm_change_interp(i_name, bprm); + if (retval < 0) + return retval; + + /* + * OK, now restart the process with the interpreter's dentry. + */ + file = open_exec(i_name); + if (IS_ERR(file)) + return PTR_ERR(file); + + bprm->interpreter = file; + return 0; +} + +static struct linux_binfmt script_format = { + .module = THIS_MODULE, + .load_binary = load_script, +}; + +static int __init init_script_binfmt(void) +{ + register_binfmt(&script_format); + return 0; +} + +static void __exit exit_script_binfmt(void) +{ + unregister_binfmt(&script_format); +} + +core_initcall(init_script_binfmt); +module_exit(exit_script_binfmt); +MODULE_LICENSE("GPL"); |