4.19-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
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@linutronix.de Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@kernel.org Link: https://lore.kernel.org/r/ZT6narvE%2BLxX%2B7Be@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 @@ -690,8 +690,8 @@ void *__init_or_module text_poke_early(v } 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