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    Subject[PATCH 5.6 049/106] cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled
    Date
    From: Toke Høiland-Jørgensen <toke@redhat.com>

    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 <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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    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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