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, 163 insertions, 0 deletions

diff --git a/net/sched/em_text.c b/net/sched/em_text.c
new file mode 100644
index 000000000..343f1aebe
--- /dev/null
+++ b/net/sched/em_text.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * net/sched/em_text.c	Textsearch ematch
+ *
+ * Authors:	Thomas Graf <tgraf@suug.ch>
+ */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/skbuff.h>
+#include <linux/textsearch.h>
+#include <linux/tc_ematch/tc_em_text.h>
+#include <net/pkt_cls.h>
+
+struct text_match {
+	u16			from_offset;
+	u16			to_offset;
+	u8			from_layer;
+	u8			to_layer;
+	struct ts_config	*config;
+};
+
+#define EM_TEXT_PRIV(m) ((struct text_match *) (m)->data)
+
+static int em_text_match(struct sk_buff *skb, struct tcf_ematch *m,
+			 struct tcf_pkt_info *info)
+{
+	struct text_match *tm = EM_TEXT_PRIV(m);
+	unsigned char *ptr;
+	int from, to;
+
+	ptr = tcf_get_base_ptr(skb, tm->from_layer);
+	if (!ptr)
+		return 0;
+	from = ptr - skb->data;
+	from += tm->from_offset;
+
+	ptr = tcf_get_base_ptr(skb, tm->to_layer);
+	if (!ptr)
+		return 0;
+	to = ptr - skb->data;
+	to += tm->to_offset;
+
+	return skb_find_text(skb, from, to, tm->config) != UINT_MAX;
+}
+
+static int em_text_change(struct net *net, void *data, int len,
+			  struct tcf_ematch *m)
+{
+	struct text_match *tm;
+	struct tcf_em_text *conf = data;
+	struct ts_config *ts_conf;
+	int flags = 0;
+
+	if (len < sizeof(*conf) || len < (sizeof(*conf) + conf->pattern_len))
+		return -EINVAL;
+
+	if (conf->from_layer > conf->to_layer)
+		return -EINVAL;
+
+	if (conf->from_layer == conf->to_layer &&
+	    conf->from_offset > conf->to_offset)
+		return -EINVAL;
+
+retry:
+	ts_conf = textsearch_prepare(conf->algo, (u8 *) conf + sizeof(*conf),
+				     conf->pattern_len, GFP_KERNEL, flags);
+
+	if (flags & TS_AUTOLOAD)
+		rtnl_lock();
+
+	if (IS_ERR(ts_conf)) {
+		if (PTR_ERR(ts_conf) == -ENOENT && !(flags & TS_AUTOLOAD)) {
+			rtnl_unlock();
+			flags |= TS_AUTOLOAD;
+			goto retry;
+		} else
+			return PTR_ERR(ts_conf);
+	} else if (flags & TS_AUTOLOAD) {
+		textsearch_destroy(ts_conf);
+		return -EAGAIN;
+	}
+
+	tm = kmalloc_obj(*tm);
+	if (tm == NULL) {
+		textsearch_destroy(ts_conf);
+		return -ENOBUFS;
+	}
+
+	tm->from_offset = conf->from_offset;
+	tm->to_offset   = conf->to_offset;
+	tm->from_layer  = conf->from_layer;
+	tm->to_layer    = conf->to_layer;
+	tm->config      = ts_conf;
+
+	m->datalen = sizeof(*tm);
+	m->data = (unsigned long) tm;
+
+	return 0;
+}
+
+static void em_text_destroy(struct tcf_ematch *m)
+{
+	if (EM_TEXT_PRIV(m) && EM_TEXT_PRIV(m)->config) {
+		textsearch_destroy(EM_TEXT_PRIV(m)->config);
+		kfree(EM_TEXT_PRIV(m));
+	}
+}
+
+static int em_text_dump(struct sk_buff *skb, struct tcf_ematch *m)
+{
+	struct text_match *tm = EM_TEXT_PRIV(m);
+	struct tcf_em_text conf;
+
+	strscpy(conf.algo, tm->config->ops->name);
+	conf.from_offset = tm->from_offset;
+	conf.to_offset = tm->to_offset;
+	conf.from_layer = tm->from_layer;
+	conf.to_layer = tm->to_layer;
+	conf.pattern_len = textsearch_get_pattern_len(tm->config);
+	conf.pad = 0;
+
+	if (nla_put_nohdr(skb, sizeof(conf), &conf) < 0)
+		goto nla_put_failure;
+	if (nla_append(skb, conf.pattern_len,
+		       textsearch_get_pattern(tm->config)) < 0)
+		goto nla_put_failure;
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
+static struct tcf_ematch_ops em_text_ops = {
+	.kind	  = TCF_EM_TEXT,
+	.change	  = em_text_change,
+	.match	  = em_text_match,
+	.destroy  = em_text_destroy,
+	.dump	  = em_text_dump,
+	.owner	  = THIS_MODULE,
+	.link	  = LIST_HEAD_INIT(em_text_ops.link)
+};
+
+static int __init init_em_text(void)
+{
+	return tcf_em_register(&em_text_ops);
+}
+
+static void __exit exit_em_text(void)
+{
+	tcf_em_unregister(&em_text_ops);
+}
+
+MODULE_DESCRIPTION("ematch classifier for embedded text in skbs");
+MODULE_LICENSE("GPL");
+
+module_init(init_em_text);
+module_exit(exit_em_text);
+
+MODULE_ALIAS_TCF_EMATCH(TCF_EM_TEXT);