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SubjectRe: [patch V3 00/20] x86/iopl: Prevent user space from using CLI/STI with iopl(3)
On Wed, Nov 13, 2019 at 09:42:40PM +0100, Thomas Gleixner wrote:

> iopl(level = 3) enables aside of access to all 65536 I/O ports also the
> usage of CLI/STI in user space.
>
> Disabling interrupts in user space can lead to system lockups and breaks
> assumptions in the kernel that userspace always runs with interrupts
> enabled.
>
> iopl() is often preferred over ioperm() as it avoids the overhead of
> copying the tasks I/O bitmap to the TSS bitmap on context switch. This
> overhead can be avoided by providing a all zeroes bitmap in the TSS and
> switching the TSS bitmap offset to this permit all IO bitmap. It's
> marginally slower than iopl() which is a one time setup, but prevents the
> usage of CLI/STI in user space.

> ---
> arch/x86/Kconfig | 18 ++
> arch/x86/entry/common.c | 4
> arch/x86/include/asm/io_bitmap.h | 29 ++++
> arch/x86/include/asm/paravirt.h | 4
> arch/x86/include/asm/paravirt_types.h | 2
> arch/x86/include/asm/pgtable_32_types.h | 2
> arch/x86/include/asm/processor.h | 113 ++++++++++-------
> arch/x86/include/asm/ptrace.h | 6
> arch/x86/include/asm/switch_to.h | 10 +
> arch/x86/include/asm/thread_info.h | 14 +-
> arch/x86/include/asm/xen/hypervisor.h | 2
> arch/x86/kernel/cpu/common.c | 188 ++++++++++++----------------
> arch/x86/kernel/doublefault.c | 2
> arch/x86/kernel/ioport.c | 209 +++++++++++++++++++++-----------
> arch/x86/kernel/paravirt.c | 2
> arch/x86/kernel/process.c | 200 ++++++++++++++++++++++++------
> arch/x86/kernel/process_32.c | 77 -----------
> arch/x86/kernel/process_64.c | 86 -------------
> arch/x86/kernel/ptrace.c | 12 +
> arch/x86/kvm/vmx/vmx.c | 8 -
> arch/x86/mm/cpu_entry_area.c | 8 +
> arch/x86/xen/enlighten_pv.c | 10 -
> tools/testing/selftests/x86/ioperm.c | 16 ++
> tools/testing/selftests/x86/iopl.c | 129 ++++++++++++++++++-
> 24 files changed, 674 insertions(+), 477 deletions(-)


Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

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