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    Subject[PATCH v2 7/7] ARM: mm: Fix PXN process with LPAE feature
    Date
    When user code execution with privilege mode, it will lead to
    infinite loop in the page fault handler if ARM_LPAE enabled,

    The issue could be reproduced with
    "echo EXEC_USERSPACE > /sys/kernel/debug/provoke-crash/DIRECT"

    Lets' fix it by adding the check in do_page_fault() and panic
    when ARM_LPAE enabled.

    Fixes: 1d4d37159d01 ("ARM: 8235/1: Support for the PXN CPU feature on ARMv7")
    Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
    ---
    arch/arm/mm/fault.c | 8 +++++++-
    1 file changed, 7 insertions(+), 1 deletion(-)

    diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
    index 7cfa9a59d3ec..279bbeb33b48 100644
    --- a/arch/arm/mm/fault.c
    +++ b/arch/arm/mm/fault.c
    @@ -257,8 +257,14 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
    vm_flags = VM_WRITE;
    }

    - if (fsr & FSR_LNX_PF)
    + if (fsr & FSR_LNX_PF) {
    vm_flags = VM_EXEC;
    +#ifdef CONFIG_ARM_LPAE
    + if (addr && addr < TASK_SIZE && !user_mode(regs))
    + die_kernel_fault("execution of user memory",
    + addr, fsr, regs);
    +#endif
    + }

    perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

    --
    2.26.2
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