Commit e14fd4ba authored Dec 22, 2020 by Andi Kleen Committed by Linus Torvalds Dec 22, 2020

x86/split-lock: Avoid returning with interrupts enabled



When a split lock is detected always make sure to disable interrupts
before returning from the trap handler.

The kernel exit code assumes that all exits run with interrupts
disabled, otherwise the SWAPGS sequence can race against interrupts and
cause recursing page faults and later panics.

The problem will only happen on CPUs with split lock disable
functionality, so Icelake Server, Tiger Lake, Snow Ridge, Jacobsville.

Fixes: ca4c6a98 ("x86/traps: Make interrupt enable/disable symmetric in C code")
Fixes: bce9b042 ("x86/traps: Disable interrupts in exc_aligment_check()") # v5.8+
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 8653b778

arch/x86/kernel/traps.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -303,11 +303,12 @@ DEFINE_IDTENTRY_ERRORCODE(exc_alignment_check)
		local_irq_enable();

		if (handle_user_split_lock(regs, error_code))
		return;
		goto out;

		do_trap(X86_TRAP_AC, SIGBUS, "alignment check", regs,
		error_code, BUS_ADRALN, NULL);

		out:
		local_irq_disable();
		}

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