5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
commit 3ea1704a92967834bf0e64ca1205db4680d04048 upstream.
text_poke_early() does:
local_irq_save(flags);
memcpy(addr, opcode, len);
local_irq_restore(flags);
sync_core();
That's not really correct because the synchronization should happen before
interrupts are re-enabled to ensure that a pending interrupt observes the
complete update of the opcodes.
It's not entirely clear whether the interrupt entry provides enough
serialization already, but moving the sync_core() invocation into interrupt
disabled region does no harm and is obviously correct.
Fixes: 6fffacb30349 ("x86/alternatives, jumplabel: Use text_poke_early() before mm_init()")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Link: https://lore.kernel.org/r/ZT6narvE%2BLxX%2B7Be@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/alternative.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -772,8 +772,8 @@ void __init_or_module text_poke_early(vo
} else {
local_irq_save(flags);
memcpy(addr, opcode, len);
- local_irq_restore(flags);
sync_core();
+ local_irq_restore(flags);
/*
* Could also do a CLFLUSH here to speed up CPU recovery; but
