[PATCH AUTOSEL 4.19 21/30] cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled

[Sasha Levin <sashal@kernel.org>]

From: Toke Høiland-Jørgensen <toke@redhat.com>

[ Upstream commit bc23d0e3f717ced21fbfacab3ab887d55e5ba367 ]

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 <xmu@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Xiumei Mu <xmu@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200416083120.453718-1-toke@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/bpf/cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 3c18260403dde..61fbcae82f0a1 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -455,7 +455,7 @@ static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
 		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) {
-- 
2.20.1