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    Subject[PATCH 1/2] x86/MCE/AMD: Check for NULL banks in THR interrupt handler
    Date
    From: Yazen Ghannam <yazen.ghannam@amd.com>

    If threshold_init_device() fails then per_cpu(threshold_banks) will be
    deallocated. The thresholding interrupt handler will still be active, so
    it's possible to get a NULL pointer dereference if a THR interrupt
    happens and any of the structures are NULL.

    Exit the handler if per_cpu(threshold_banks) is NULL and skip NULL
    banks. MCA error information will still be in the registers. The
    information will be logged during polling or in another MCA exception or
    interrupt handler.

    Fixes: 17ef4af0ec0f ("x86/mce/AMD: Use saved threshold block info in interrupt handler")
    Cc: <stable@vger.kernel.org> # 4.13.x
    Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
    ---
    arch/x86/kernel/cpu/mcheck/mce_amd.c | 10 +++++++++-
    1 file changed, 9 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
    index dd33c357548f..2dbf34250bbf 100644
    --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
    +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
    @@ -934,13 +934,21 @@ static void log_and_reset_block(struct threshold_block *block)
    static void amd_threshold_interrupt(void)
    {
    struct threshold_block *first_block = NULL, *block = NULL, *tmp = NULL;
    + struct threshold_bank *th_bank = NULL;
    unsigned int bank, cpu = smp_processor_id();

    + if (!per_cpu(threshold_banks, cpu))
    + return;
    +
    for (bank = 0; bank < mca_cfg.banks; ++bank) {
    if (!(per_cpu(bank_map, cpu) & (1 << bank)))
    continue;

    - first_block = per_cpu(threshold_banks, cpu)[bank]->blocks;
    + th_bank = per_cpu(threshold_banks, cpu)[bank];
    + if (!th_bank)
    + continue;
    +
    + first_block = th_bank->blocks;
    if (!first_block)
    continue;

    --
    2.17.1
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