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-rw-r--r--fs/binfmt_script.c158
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");