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, 99 insertions, 0 deletions

diff --git a/security/landlock/errata.h b/security/landlock/errata.h
new file mode 100644
index 000000000..8e626acca
--- /dev/null
+++ b/security/landlock/errata.h
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock - Errata information
+ *
+ * Copyright © 2025 Microsoft Corporation
+ */
+
+#ifndef _SECURITY_LANDLOCK_ERRATA_H
+#define _SECURITY_LANDLOCK_ERRATA_H
+
+#include <linux/init.h>
+
+struct landlock_erratum {
+	const int abi;
+	const u8 number;
+};
+
+/* clang-format off */
+#define LANDLOCK_ERRATUM(NUMBER) \
+	{ \
+		.abi = LANDLOCK_ERRATA_ABI, \
+		.number = NUMBER, \
+	},
+/* clang-format on */
+
+/*
+ * Some fixes may require user space to check if they are applied on the running
+ * kernel before using a specific feature.  For instance, this applies when a
+ * restriction was previously too restrictive and is now getting relaxed (for
+ * compatibility or semantic reasons).  However, non-visible changes for
+ * legitimate use (e.g. security fixes) do not require an erratum.
+ */
+static const struct landlock_erratum landlock_errata_init[] __initconst = {
+
+/*
+ * Only Sparse may not implement __has_include.  If a compiler does not
+ * implement __has_include, a warning will be printed at boot time (see
+ * setup.c).
+ */
+#ifdef __has_include
+
+#define LANDLOCK_ERRATA_ABI 1
+#if __has_include("errata/abi-1.h")
+#include "errata/abi-1.h"
+#endif
+#undef LANDLOCK_ERRATA_ABI
+
+#define LANDLOCK_ERRATA_ABI 2
+#if __has_include("errata/abi-2.h")
+#include "errata/abi-2.h"
+#endif
+#undef LANDLOCK_ERRATA_ABI
+
+#define LANDLOCK_ERRATA_ABI 3
+#if __has_include("errata/abi-3.h")
+#include "errata/abi-3.h"
+#endif
+#undef LANDLOCK_ERRATA_ABI
+
+#define LANDLOCK_ERRATA_ABI 4
+#if __has_include("errata/abi-4.h")
+#include "errata/abi-4.h"
+#endif
+#undef LANDLOCK_ERRATA_ABI
+
+#define LANDLOCK_ERRATA_ABI 5
+#if __has_include("errata/abi-5.h")
+#include "errata/abi-5.h"
+#endif
+#undef LANDLOCK_ERRATA_ABI
+
+#define LANDLOCK_ERRATA_ABI 6
+#if __has_include("errata/abi-6.h")
+#include "errata/abi-6.h"
+#endif
+#undef LANDLOCK_ERRATA_ABI
+
+/*
+ * For each new erratum, we need to include all the ABI files up to the impacted
+ * ABI to make all potential future intermediate errata easy to backport.
+ *
+ * If such change involves more than one ABI addition, then it must be in a
+ * dedicated commit with the same Fixes tag as used for the actual fix.
+ *
+ * Each commit creating a new security/landlock/errata/abi-*.h file must have a
+ * Depends-on tag to reference the commit that previously added the line to
+ * include this new file, except if the original Fixes tag is enough.
+ *
+ * Each erratum must be documented in its related ABI file, and a dedicated
+ * commit must update Documentation/userspace-api/landlock.rst to include this
+ * erratum.  This commit will not be backported.
+ */
+
+#endif
+
+	{}
+};
+
+#endif /* _SECURITY_LANDLOCK_ERRATA_H */