From 7cded618c00ede8ed42399f7f98517547b56de7b Mon Sep 17 00:00:00 2001 From: Julien Thierry Date: Wed, 13 Feb 2019 19:53:52 +0800 Subject: [PATCH] arm64: Skip preemption when exiting an NMI hulk inclusion category: feature bugzilla: 9291 CVE: NA ported from https://lore.kernel.org/patchwork/patch/1037481/ -------------------------------- Handling of an NMI should not set any TIF flags. For NMIs received from EL0 the current exit path is safe to use. However, an NMI received at EL1 could have interrupted some task context that has set the TIF_NEED_RESCHED flag. Preempting a task should not happen as a result of an NMI. Skip preemption after handling an NMI from EL1. Signed-off-by: Julien Thierry Acked-by: Marc Zyngier Cc: Catalin Marinas Cc: Will Deacon Cc: Marc Zyngier Signed-off-by: Wei Li Reviewed-by: Hanjun Guo Signed-off-by: Yang Yingliang --- arch/arm64/kernel/entry.S | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 9d61daba3929..43a91e060448 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -637,7 +637,15 @@ el1_irq: #ifdef CONFIG_PREEMPT ldr w24, [tsk, #TSK_TI_PREEMPT] // get preempt count - cbnz w24, 1f // preempt count != 0 +alternative_if ARM64_HAS_IRQ_PRIO_MASKING + /* + * DA_F were cleared at start of handling. If anything is set in DAIF, + * we come back from an NMI, so skip preemption + */ + mrs x0, daif + orr w24, w24, w0 +alternative_else_nop_endif + cbnz w24, 1f // preempt count != 0 || NMI return path ldr x0, [tsk, #TSK_TI_FLAGS] // get flags tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling? bl el1_preempt -- GitLab