arm64: fix NULL dereference in have_cpu_die()

commit 335d2c2d192266358c5dfa64953a4c162f46e464 upstream.

Commit 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are
stuck in the kernel") added a helper function to determine if die() is
supported in cpu_ops. This function assumes a cpu will have a valid
cpu_ops entry, but that may not be the case for cpu0 is spin-table or
parking protocol is used to boot secondary cpus. In that case, there
is a NULL dereference if have_cpu_die() is called by cpu0. So add a
check for a valid cpu_ops before dereferencing it.

Fixes: 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are stuck in the kernel")
Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 8507703..a70f7d3 100644 (file)
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -934,7 +934,7 @@ static bool have_cpu_die(void)
 #ifdef CONFIG_HOTPLUG_CPU
        int any_cpu = raw_smp_processor_id();
 
-       if (cpu_ops[any_cpu]->cpu_die)
+       if (cpu_ops[any_cpu] && cpu_ops[any_cpu]->cpu_die)
                return true;
 #endif
        return false;