arm64: fix CONFIG_DEBUG_WX address reporting

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-artful' to 'verification-done-artful'. If the problem still exists, change the tag 'verification-needed-artful' to 'verification-failed-artful'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

ubuntu@hotdog:~$ dmesg | grep W+X
[ 35.653992] arm64/mm: Found insecure W+X mapping at address ffff000000ac9000/0xffff000000ac9000
[ 36.046414] Checked W+X mappings: FAILED, 12 W+X pages found, 0 non-UXN pages found

Yep, that's in the userspace mapping.

This bug was fixed in the package linux - 4.13.0-43.48

---------------
linux (4.13.0-43.48) artful; urgency=medium

  * CVE-2018-3639 (powerpc)
    - SAUCE: rfi-flush: update H_CPU_* macro names to upstream
    - SAUCE: rfi-flush: update plpar_get_cpu_characteristics() signature to
      upstream
    - SAUCE: update pseries_setup_rfi_flush() capitalization to upstream
    - powerpc/pseries: Support firmware disable of RFI flush
    - powerpc/powernv: Support firmware disable of RFI flush
    - powerpc/64s: Allow control of RFI flush via debugfs
    - powerpc/rfi-flush: Move the logic to avoid a redo into the debugfs code
    - powerpc/rfi-flush: Always enable fallback flush on pseries
    - powerpc/rfi-flush: Differentiate enabled and patched flush types
    - powerpc/pseries: Add new H_GET_CPU_CHARACTERISTICS flags
    - powerpc: Add security feature flags for Spectre/Meltdown
    - powerpc/powernv: Set or clear security feature flags
    - powerpc/pseries: Set or clear security feature flags
    - powerpc/powernv: Use the security flags in pnv_setup_rfi_flush()
    - powerpc/pseries: Use the security flags in pseries_setup_rfi_flush()
    - powerpc/pseries: Fix clearing of security feature flags
    - powerpc: Move default security feature flags
    - powerpc/pseries: Restore default security feature flags on setup
    - powerpc/64s: Add support for a store forwarding barrier at kernel entry/exit

  * CVE-2018-3639 (x86)
    - SAUCE: Add X86_FEATURE_ARCH_CAPABILITIES
    - SAUCE: x86: Add alternative_msr_write
    - x86/nospec: Simplify alternative_msr_write()
    - x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
    - x86/bugs: Concentrate bug detection into a separate function
    - x86/bugs: Concentrate bug reporting into a separate function
    - x86/msr: Add definitions for new speculation control MSRs
    - x86/bugs: Read SPEC_CTRL MSR during boot and re-use reserved bits
    - x86/bugs, KVM: Support the combination of guest and host IBRS
    - x86/bugs: Expose /sys/../spec_store_bypass
    - x86/cpufeatures: Add X86_FEATURE_RDS
    - x86/bugs: Provide boot parameters for the spec_store_bypass_disable
      mitigation
    - x86/bugs/intel: Set proper CPU features and setup RDS
    - x86/bugs: Whitelist allowed SPEC_CTRL MSR values
    - x86/bugs/AMD: Add support to disable RDS on Fam[15,16,17]h if requested
    - x86/KVM/VMX: Expose SPEC_CTRL Bit(2) to the guest
    - x86/speculation: Create spec-ctrl.h to avoid include hell
    - prctl: Add speculation control prctls
    - x86/process: Allow runtime control of Speculative Store Bypass
    - x86/speculation: Add prctl for Speculative Store Bypass mitigation
    - nospec: Allow getting/setting on non-current task
    - proc: Provide details on speculation flaw mitigations
    - seccomp: Enable speculation flaw mitigations
    - SAUCE: x86/bugs: Honour SPEC_CTRL default
    - x86/bugs: Make boot modes __ro_after_init
    - prctl: Add force disable speculation
    - seccomp: Use PR_SPEC_FORCE_DISABLE
    - seccomp: Add filter flag to opt-out of SSB mitigation
    - seccomp: Move speculation migitation control to arch code
    - x86/speculation: Make "seccomp" the...