ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 159 insertions, 0 deletions

diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c
new file mode 100644
index 000000000..637daf6e4
--- /dev/null
+++ b/fs/binfmt_script.c
@@ -0,0 +1,159 @@
+// 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_DESCRIPTION("Kernel support for scripts starting with #!");
+MODULE_LICENSE("GPL");