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From:   Wei Li <liwei391@huawei.com>
To:     <julien.thierry@arm.com>, <linux-arm-kernel@lists.infradead.org>
CC:     <linux-kernel@vger.kernel.org>, <marc.zyngier@arm.com>,
        <daniel.thompson@linaro.org>, <catalin.marinas@arm.com>,
        <will.deacon@arm.com>, <dave.martin@arm.com>,
        <mark.rutland@arm.com>, <jason@lakedaemon.net>,
        <huawei.libin@huawei.com>, <guohanjun@huawei.com>,
        <thunder.leizhen@huawei.com>
Subject: [PATCH] arm64: fix potential deadlock in arm64-provide-pseudo-NMI-with-GICv3
Date:   Tue, 29 Jan 2019 21:12:23 +0800
Message-ID: <20190129131223.32505-1-liwei391@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In some exception handlers, the interrupt is not reenabled by daifclr at first.
The later process may call local_irq_enable() to enable the interrupt, like
gic_handle_irq(). As we known, function local_irq_enable() just change the pmr now.
The following codes what i found may cause a deadlock or some issues else:

do_sp_pc_abort			<- el0_sp_pc
do_el0_ia_bp_hardening	<- el0_ia
kgdb_roundup_cpus		<- el1_dbg

Signed-off-by: Wei Li <liwei391@huawei.com>
---
 arch/arm64/kernel/kgdb.c | 4 ++++
 arch/arm64/mm/fault.c    | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
index a20de58061a8..119fbf2c0788 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c
@@ -25,6 +25,7 @@
 #include <linux/kgdb.h>
 #include <linux/kprobes.h>
 #include <linux/sched/task_stack.h>
+#include <linux/irqchip/arm-gic-v3.h>
 
 #include <asm/debug-monitors.h>
 #include <asm/insn.h>
@@ -291,6 +292,9 @@ static void kgdb_call_nmi_hook(void *ignored)
 
 void kgdb_roundup_cpus(unsigned long flags)
 {
+	if (gic_prio_masking_enabled())
+		gic_arch_enable_irqs();
+
 	local_irq_enable();
 	smp_call_function(kgdb_call_nmi_hook, NULL, 0);
 	local_irq_disable();
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 97ba2ba78aee..f7c39a0b28bc 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -32,6 +32,7 @@
 #include <linux/perf_event.h>
 #include <linux/preempt.h>
 #include <linux/hugetlb.h>
+#include <linux/irqchip/arm-gic-v3.h>
 
 #include <asm/bug.h>
 #include <asm/cmpxchg.h>
@@ -780,6 +781,8 @@ asmlinkage void __exception do_el0_ia_bp_hardening(unsigned long addr,
 	if (addr > TASK_SIZE)
 		arm64_apply_bp_hardening();
 
+	if (gic_prio_masking_enabled())
+		gic_arch_enable_irqs();
 	local_irq_enable();
 	do_mem_abort(addr, esr, regs);
 }
@@ -794,6 +797,9 @@ asmlinkage void __exception do_sp_pc_abort(unsigned long addr,
 	if (user_mode(regs)) {
 		if (instruction_pointer(regs) > TASK_SIZE)
 			arm64_apply_bp_hardening();
+
+		if (gic_prio_masking_enabled())
+			gic_arch_enable_irqs();
 		local_irq_enable();
 	}
 
-- 
2.17.1