Messages in this thread | | | Date | Thu, 14 Nov 2019 19:13:24 +0100 | From | Borislav Petkov <> | Subject | Re: [patch V3 17/20] x86/iopl: Restrict iopl() permission scope |
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On Wed, Nov 13, 2019 at 09:42:57PM +0100, Thomas Gleixner wrote: > From: Thomas Gleixner <tglx@linutronix.de> > > The access to the full I/O port range can be also provided by the TSS I/O > bitmap, but that would require to copy 8k of data on scheduling in the > task. As shown with the sched out optimization TSS.io_bitmap_base can be > used to switch the incoming task to a preallocated I/O bitmap which has all > bits zero, i.e. allows access to all I/O ports. > > Implementing this allows to provide an iopl() emulation mode which restricts > the IOPL level 3 permissions to I/O port access but removes the STI/CLI > permission which is coming with the hardware IOPL mechansim. > > Provide a config option to switch IOPL to emulation mode, make it the > default and while at it also provide an option to disable IOPL completely. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Acked-by: Andy Lutomirski <luto@kernel.org> > --- > V3: Folded the missing NULL pointer check, reduced preempt disable > scope (Ingo) > > V2: Fixed the 32bit build fail by increasing the cpu entry area size > Move the TSS update out of the iopl() emulation code. > --- > arch/x86/Kconfig | 32 +++++++++++ > arch/x86/include/asm/pgtable_32_types.h | 2 > arch/x86/include/asm/processor.h | 28 +++++++--- > arch/x86/kernel/cpu/common.c | 5 + > arch/x86/kernel/ioport.c | 87 ++++++++++++++++++++++---------- > arch/x86/kernel/process.c | 28 ++++++---- > 6 files changed, 137 insertions(+), 45 deletions(-) > > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1254,6 +1254,38 @@ config X86_VSYSCALL_EMULATION > Disabling this option saves about 7K of kernel size and > possibly 4K of additional runtime pagetable memory. > > +choice > + prompt "IOPL" > + default X86_IOPL_EMULATION > + > +config X86_IOPL_EMULATION > + bool "IOPL Emulation" > + ---help--- > + Legacy IOPL support is an overbroad mechanism which allows user > + space aside of accessing all 65536 I/O ports also to disable > + interrupts. To gain this access the caller needs CAP_SYS_RAWIO > + capabilities and permission from eventually active security
I think you mean here: s/eventually/potentially/ or so. "eventually" is one of the false friends. :)
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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