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    Subject[47/98] x86, AMD: Fix stale cpuid4_info shared_map data in shared_cpu_map cpumasks
    2.6.32-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Prarit Bhargava <prarit@redhat.com>

    commit ebb682f522411abbe358059a256a8672ec0bd55b upstream.

    The per_cpu cpuid4_info shared_map can contain stale data when CPUs are added
    and removed.

    The stale data can lead to a NULL pointer derefernce panic on a remove of a
    CPU that has had siblings previously removed.

    This patch resolves the panic by verifying a cpu is actually online before
    adding it to the shared_cpu_map, only examining cpus that are part of
    the same lower level cache, and by updating other siblings lowest level cache
    maps when a cpu is added.

    Signed-off-by: Prarit Bhargava <prarit@redhat.com>
    LKML-Reference: <20091209183336.17855.98708.sendpatchset@prarit.bos.redhat.com>
    Signed-off-by: H. Peter Anvin <hpa@zytor.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86/kernel/cpu/intel_cacheinfo.c | 13 +++++++------
    1 file changed, 7 insertions(+), 6 deletions(-)

    --- a/arch/x86/kernel/cpu/intel_cacheinfo.c
    +++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
    @@ -647,18 +647,19 @@ static void __cpuinit cache_shared_cpu_m
    {
    struct _cpuid4_info *this_leaf, *sibling_leaf;
    unsigned long num_threads_sharing;
    - int index_msb, i;
    + int index_msb, i, sibling;
    struct cpuinfo_x86 *c = &cpu_data(cpu);

    if ((index == 3) && (c->x86_vendor == X86_VENDOR_AMD)) {
    - struct cpuinfo_x86 *d;
    - for_each_online_cpu(i) {
    + for_each_cpu(i, c->llc_shared_map) {
    if (!per_cpu(cpuid4_info, i))
    continue;
    - d = &cpu_data(i);
    this_leaf = CPUID4_INFO_IDX(i, index);
    - cpumask_copy(to_cpumask(this_leaf->shared_cpu_map),
    - d->llc_shared_map);
    + for_each_cpu(sibling, c->llc_shared_map) {
    + if (!cpu_online(sibling))
    + continue;
    + set_bit(sibling, this_leaf->shared_cpu_map);
    + }
    }
    return;
    }



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