[patch] x86, numa: Add error handling for bad cpu-to-node mappings

[David Rientjes]

CONFIG_DEBUG_PER_CPU_MAPS may return NUMA_NO_NODE when an
early_cpu_to_node() mapping hasn't been initialized.  In such a case, it
emits a warning and continues without an issue but callers may try to use
the return value to index into an array.

We can catch those errors and fail silently since a warning has already
been emitted.  No current user of numa_add_cpu() requires this error
checking to avoid a crash, but it's better to be proactive in case a
future user happens to have a bug and a user tries to diagnose it with
CONFIG_DEBUG_PER_CPU_MAPS.

Reported-by: Jesper Juhl <jj@xxxxxxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
 arch/x86/mm/numa.c    |    4 ++++
 arch/x86/mm/numa_64.c |    4 ++++
 2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -219,6 +219,10 @@ struct cpumask __cpuinit *debug_cpumask_set_cpu(int cpu, int enable)
 	struct cpumask *mask;
 	char buf[64];
 
+	if (node == NUMA_NO_NODE) {
+		/* early_cpu_to_node() already emits a warning and trace */
+		return NULL;
+	}
 	mask = node_to_cpumask_map[node];
 	if (!mask) {
 		pr_err("node_to_cpumask_map[%i] NULL\n", node);
diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -709,6 +709,10 @@ static void __cpuinit numa_set_cpumask(int cpu, int enable)
 	struct cpumask *mask;
 	int i;
 
+	if (node == NUMA_NO_NODE) {
+		/* early_cpu_to_node() already emits a warning and trace */
+		return;
+	}
 	for_each_online_node(i) {
 		unsigned long addr;
 
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