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x86/alternatives: Sync core before enabling interrupts

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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: 6fffacb303 ("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>
This commit is contained in:
Thomas Gleixner 2023-12-07 20:49:24 +01:00 committed by Greg Kroah-Hartman
parent f08531dd7c
commit 8f6f8443a2
1 changed files with 1 additions and 1 deletions
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arch/x86/kernel/alternative.c
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@ -690,8 +690,8 @@ void *__init_or_module text_poke_early(void *addr, const void *opcode,
} 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