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, 119 insertions, 0 deletions

diff --git a/security/ipe/digest.c b/security/ipe/digest.c
new file mode 100644
index 000000000..6e597a6b7
--- /dev/null
+++ b/security/ipe/digest.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2024 Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/hex.h>
+#include "digest.h"
+
+/**
+ * ipe_digest_parse() - parse a digest in IPE's policy.
+ * @valstr: Supplies the string parsed from the policy.
+ *
+ * Digests in IPE are defined in a standard way:
+ *	<alg_name>:<hex>
+ *
+ * Use this function to create a property to parse the digest
+ * consistently. The parsed digest will be saved in @value in IPE's
+ * policy.
+ *
+ * Return: The parsed digest_info structure on success. If an error occurs,
+ * the function will return the error value (via ERR_PTR).
+ */
+struct digest_info *ipe_digest_parse(const char *valstr)
+{
+	struct digest_info *info = NULL;
+	char *sep, *raw_digest;
+	size_t raw_digest_len;
+	u8 *digest = NULL;
+	char *alg = NULL;
+	int rc = 0;
+
+	info = kzalloc_obj(*info);
+	if (!info)
+		return ERR_PTR(-ENOMEM);
+
+	sep = strchr(valstr, ':');
+	if (!sep) {
+		rc = -EBADMSG;
+		goto err;
+	}
+
+	alg = kstrndup(valstr, sep - valstr, GFP_KERNEL);
+	if (!alg) {
+		rc = -ENOMEM;
+		goto err;
+	}
+
+	raw_digest = sep + 1;
+	raw_digest_len = strlen(raw_digest);
+
+	info->digest_len = (raw_digest_len + 1) / 2;
+	digest = kzalloc(info->digest_len, GFP_KERNEL);
+	if (!digest) {
+		rc = -ENOMEM;
+		goto err;
+	}
+
+	rc = hex2bin(digest, raw_digest, info->digest_len);
+	if (rc < 0) {
+		rc = -EINVAL;
+		goto err;
+	}
+
+	info->alg = alg;
+	info->digest = digest;
+	return info;
+
+err:
+	kfree(alg);
+	kfree(digest);
+	kfree(info);
+	return ERR_PTR(rc);
+}
+
+/**
+ * ipe_digest_eval() - evaluate an IPE digest against another digest.
+ * @expected: Supplies the policy-provided digest value.
+ * @digest: Supplies the digest to compare against the policy digest value.
+ *
+ * Return:
+ * * %true	- digests match
+ * * %false	- digests do not match
+ */
+bool ipe_digest_eval(const struct digest_info *expected,
+		     const struct digest_info *digest)
+{
+	return (expected->digest_len == digest->digest_len) &&
+	       (!strcmp(expected->alg, digest->alg)) &&
+	       (!memcmp(expected->digest, digest->digest, expected->digest_len));
+}
+
+/**
+ * ipe_digest_free() - free an IPE digest.
+ * @info: Supplies a pointer the policy-provided digest to free.
+ */
+void ipe_digest_free(struct digest_info *info)
+{
+	if (IS_ERR_OR_NULL(info))
+		return;
+
+	kfree(info->alg);
+	kfree(info->digest);
+	kfree(info);
+}
+
+/**
+ * ipe_digest_audit() - audit a digest that was sourced from IPE's policy.
+ * @ab: Supplies the audit_buffer to append the formatted result.
+ * @info: Supplies a pointer to source the audit record from.
+ *
+ * Digests in IPE are audited in this format:
+ *	<alg_name>:<hex>
+ */
+void ipe_digest_audit(struct audit_buffer *ab, const struct digest_info *info)
+{
+	audit_log_untrustedstring(ab, info->alg);
+	audit_log_format(ab, ":");
+	audit_log_n_hex(ab, info->digest, info->digest_len);
+}