x86/alternatives: Sync core before enabling interrupts
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>
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@ -1080,8 +1080,8 @@ void __init_or_module text_poke_early(void *addr, const void *opcode,
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} else {
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local_irq_save(flags);
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memcpy(addr, opcode, len);
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local_irq_restore(flags);
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sync_core();
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local_irq_restore(flags);
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/*
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* Could also do a CLFLUSH here to speed up CPU recovery; but
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