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From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
To: Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>, Catalin
 Marinas <catalin.marinas@arm.com>, <linux-acpi@vger.kernel.org>,
	<linux-arch@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
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CC: Mark Rutland <mark.rutland@arm.com>, Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>, <loongarch@lists.linux.dev>,
	<x86@kernel.org>, Russell King <linux@armlinux.org.uk>, "Rafael J . Wysocki"
	<rafael@kernel.org>, Miguel Luis <miguel.luis@oracle.com>, James Morse
	<james.morse@arm.com>, Salil Mehta <salil.mehta@huawei.com>, Jean-Philippe
 Brucker <jean-philippe@linaro.org>, Hanjun Guo <guohanjun@huawei.com>, Gavin
 Shan <gshan@redhat.com>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov
	<bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>,
	<linuxarm@huawei.com>, <justin.he@arm.com>, <jianyong.wu@arm.com>
Subject: [PATCH v10 12/19] arm64: acpi: Harden get_cpu_for_acpi_id() against missing CPU entry
Date: Wed, 29 May 2024 14:34:39 +0100
Message-ID: <20240529133446.28446-13-Jonathan.Cameron@huawei.com>
In-Reply-To: <20240529133446.28446-1-Jonathan.Cameron@huawei.com>
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In a review discussion of the changes to support vCPU hotplug where
a check was added on the GICC being enabled if was online, it was
noted that there is need to map back to the cpu and use that to index
into a cpumask. As such, a valid ID is needed.

If an MPIDR check fails in acpi_map_gic_cpu_interface() it is possible
for the entry in cpu_madt_gicc[cpu] == NULL.  This function would
then cause a NULL pointer dereference.   Whilst a path to trigger
this has not been established, harden this caller against the
possibility.

Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

---
V10: Fix description above (duplicated word).
     Picked up Gavin's tag.
---
 arch/arm64/include/asm/acpi.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index bc9a6656fc0c..a407f9cd549e 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -124,7 +124,8 @@ static inline int get_cpu_for_acpi_id(u32 uid)
 	int cpu;
 
 	for (cpu = 0; cpu < nr_cpu_ids; cpu++)
-		if (uid == get_acpi_id_for_cpu(cpu))
+		if (acpi_cpu_get_madt_gicc(cpu) &&
+		    uid == get_acpi_id_for_cpu(cpu))
 			return cpu;
 
 	return -EINVAL;
-- 
2.39.2