arm64: acpi: Harden get_cpu_for_acpi_id() against missing CPU entry

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>
Link: https://lore.kernel.org/r/20240529133446.28446-13-Jonathan.Cameron@huawei.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index bc9a6656fc0c55626284279e9bb6fea17e1ec323..a407f9cd549edccfec14f476c7e53cf04912712b 100644 (file)
--- 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;