[tip: x86/alternatives] x86/alternatives: Add text_mutex) assert to smp_text_poke_batch_flush()

[tip-bot2 for Ingo Molnar]

The following commit has been merged into the x86/alternatives branch of tip:

Commit-ID:     87836af1eafc6616bde680be556f49ba3325f798
Gitweb:        https://git.kernel.org/tip/87836af1eafc6616bde680be556f49ba3325f798
Author:        Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate:    Fri, 11 Apr 2025 07:40:33 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Fri, 11 Apr 2025 11:01:34 +02:00

x86/alternatives: Add text_mutex) assert to smp_text_poke_batch_flush()

It's possible to escape the text_mutex-held assert in
smp_text_poke_batch_process() 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 smp_text_poke_batch_process()
or smp_text_poke_batch_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@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: "H . Peter Anvin" <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250411054105.2341982-22-mingo@xxxxxxxxxx
---
 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 b97abfb..c53eb3b 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 smp_text_poke_batch_flush(void *addr)
 {
+	lockdep_assert_held(&text_mutex);
+
 	if (tp_vec_nr == TP_VEC_MAX || tp_order_fail(addr)) {
 		smp_text_poke_batch_process(tp_vec, tp_vec_nr);
 		tp_vec_nr = 0;