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Date:   Fri,  1 May 2020 15:23:22 +0200
From:   Greg Kroah-Hartman <>
Cc:     Greg Kroah-Hartman <>,, Xiumei Mu <>,
        Toke Høiland-Jørgensen <>,
        Alexei Starovoitov <>,
        Jesper Dangaard Brouer <>,
        Song Liu <>
Subject: [PATCH 5.6 049/106] cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled

From: Toke Høiland-Jørgensen <>

commit bc23d0e3f717ced21fbfacab3ab887d55e5ba367 upstream.

When the kernel is built with CONFIG_DEBUG_PER_CPU_MAPS, the cpumap code
can trigger a spurious warning if CONFIG_CPUMASK_OFFSTACK is also set. This
happens because in this configuration, NR_CPUS can be larger than
nr_cpumask_bits, so the initial check in cpu_map_alloc() is not sufficient
to guard against hitting the warning in cpumask_check().

Fix this by explicitly checking the supplied key against the
nr_cpumask_bits variable before calling cpu_possible().

Fixes: 6710e1126934 ("bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP")
Reported-by: Xiumei Mu <>
Signed-off-by: Toke Høiland-Jørgensen <>
Signed-off-by: Alexei Starovoitov <>
Tested-by: Xiumei Mu <>
Acked-by: Jesper Dangaard Brouer <>
Acked-by: Song Liu <>
Signed-off-by: Greg Kroah-Hartman <>

 kernel/bpf/cpumap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -469,7 +469,7 @@ static int cpu_map_update_elem(struct bp
 		return -EOVERFLOW;
 	/* Make sure CPU is a valid possible cpu */
-	if (!cpu_possible(key_cpu))
+	if (key_cpu >= nr_cpumask_bits || !cpu_possible(key_cpu))
 		return -ENODEV;
 	if (qsize == 0) {

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