linux-kernel - [PATCH 20/41] x86/alternatives: Add text_mutex) assert to text_poke_int3

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Message-ID: <20250327205355.378659-21-mingo@kernel.org>
Date: Thu, 27 Mar 2025 21:53:33 +0100
From: Ingo Molnar <mingo@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Juergen Gross <jgross@...e.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 20/41] x86/alternatives: Add text_mutex) assert to text_poke_int3_flush()

It's possible to escape the text_mutex-held assert in
text_poke_int3_batch() if the caller uses a properly
batched and sorted series of patch requests, so add
an explicit lockdep_assert_held() to make sure it's
held by all callers.

All text_poke_int3_*() APIs will call either text_poke_int3_batch()
or text_poke_int3_flush() internally.

The text_mutex must be held, because tp_vec and tp_vec_nr et al
are all globals, and the INT3 patching machinery itself relies on
external serialization.

Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/alternative.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index a10e1b9db7b4..f75806d699be 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -2860,6 +2860,8 @@ static bool tp_order_fail(void *addr)

 static void text_poke_int3_flush(void *addr)
 {
+	lockdep_assert_held(&text_mutex);
+
 	if (tp_vec_nr == TP_VEC_MAX || tp_order_fail(addr)) {
 		text_poke_int3_batch(tp_vec, tp_vec_nr);
 		tp_vec_nr = 0;
-- 
2.45.2