From: hpa@zytor.com
To: Thomas Gleixner <tglx@linutronix.de>, Willy Tarreau <w@1wt.eu>
Cc: Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Stephen Hemminger <stephen@networkplumber.org>,
Juergen Gross <jgross@suse.com>,
Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [patch 5/9] x86/ioport: Reduce ioperm impact for sane usage further
Date: Thu, 07 Nov 2019 02:19:19 -0800 [thread overview]
Message-ID: <71DE81AC-3AD4-47B3-9CBA-A2C7841A3370@zytor.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1911071058260.4256@nanos.tec.linutronix.de>
On November 7, 2019 2:00:27 AM PST, Thomas Gleixner <tglx@linutronix.de> wrote:
>On Thu, 7 Nov 2019, Willy Tarreau wrote:
>> On Thu, Nov 07, 2019 at 09:25:41AM +0100, Ingo Molnar wrote:
>> > I.e. the model I'm suggesting is that if a task uses ioperm() or
>iopl()
>> > then it should have a bitmap from that point on until exit(), even
>if
>> > it's all zeroes or all ones. Most applications that are using those
>
>> > primitives really need it all the time and are using just a few
>ioports,
>> > so all the tracking doesn't help much anyway.
>>
>> I'd go even further, considering that any task having called ioperm()
>> or iopl() once is granted access to all 64k ports for life: if the
>task
>> was granted access to any port, it will be able to request access for
>any
>> other port anyway. And we cannot claim that finely filtering accesses
>> brings any particular reliability in my opinion, considering that
>it's
>> generally possible to make the system really sick by starting to play
>> with most I/O ports. So for me that becomes a matter of trusted vs
>not
>> trusted task. Then we can simply have two pages of 0xFF to describe
>> their I/O access bitmap.
>>
>> > On a related note, another simplification would be that in
>principle we
>> > could also use just a single bitmap and emulate iopl() as an
>ioperm(all)
>> > or ioperm(none) calls. Yeah, it's not fully ABI compatible for
>mixed
>> > ioperm()/iopl() uses, but is that ABI actually being relied on in
>> > practice?
>>
>> You mean you'd have a unified map for all tasks ? In this case I
>think
>> it's simpler and equivalent to simply ignore the values in the calls
>> and grant full perms to the 64k ports range after the calls were
>> validated. I could be totally wrong and missing something obvious
>> though.
>
>Changing ioperm(single port, port range) to be ioperm(all) is going to
>break a bunch of test cases which actually check whether the permission
>is
>restricted to a single I/O port or the requested port range.
>
>Thanks,
>
> tglx
This seems very undesirable... as much as we might wish otherwise, the port bitmap is the equivalent to the MMU, and there are definitely users doing direct device I/O out there.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
next prev parent reply other threads:[~2019-11-07 10:21 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 19:34 [patch 0/9] x86/iopl: Prevent user space from using CLI/STI with iopl(3) Thomas Gleixner
2019-11-06 19:35 ` [patch 1/9] x86/ptrace: Prevent truncation of bitmap size Thomas Gleixner
2019-11-07 7:31 ` Ingo Molnar
2019-11-06 19:35 ` [patch 2/9] x86/process: Unify copy_thread_tls() Thomas Gleixner
2019-11-08 22:31 ` Andy Lutomirski
2019-11-08 23:43 ` Thomas Gleixner
2019-11-10 12:36 ` Thomas Gleixner
2019-11-10 16:56 ` Andy Lutomirski
2019-11-11 8:52 ` Peter Zijlstra
2019-11-06 19:35 ` [patch 3/9] x86/cpu: Unify cpu_init() Thomas Gleixner
2019-11-08 22:34 ` Andy Lutomirski
2019-11-06 19:35 ` [patch 4/9] x86/io: Speedup schedule out of I/O bitmap user Thomas Gleixner
2019-11-07 9:12 ` Peter Zijlstra
2019-11-07 14:04 ` Thomas Gleixner
2019-11-07 14:08 ` Thomas Gleixner
2019-11-08 22:41 ` Andy Lutomirski
2019-11-08 23:45 ` Thomas Gleixner
2019-11-09 3:32 ` Andy Lutomirski
2019-11-10 12:43 ` Thomas Gleixner
2019-11-09 0:24 ` Andy Lutomirski
2019-11-06 19:35 ` [patch 5/9] x86/ioport: Reduce ioperm impact for sane usage further Thomas Gleixner
2019-11-07 1:11 ` Linus Torvalds
2019-11-07 7:44 ` Thomas Gleixner
2019-11-07 8:25 ` Ingo Molnar
2019-11-07 9:17 ` Willy Tarreau
2019-11-07 10:00 ` Thomas Gleixner
2019-11-07 10:13 ` Willy Tarreau
2019-11-07 10:19 ` hpa [this message]
2019-11-07 10:27 ` Willy Tarreau
2019-11-07 10:50 ` hpa
2019-11-07 12:56 ` Willy Tarreau
2019-11-07 16:45 ` Eric W. Biederman
2019-11-07 16:53 ` Linus Torvalds
2019-11-07 16:57 ` Willy Tarreau
2019-11-10 17:17 ` Andy Lutomirski
2019-11-07 7:37 ` Ingo Molnar
2019-11-07 7:45 ` Thomas Gleixner
2019-11-07 8:16 ` Ingo Molnar
2019-11-07 18:02 ` Thomas Gleixner
2019-11-07 19:24 ` Brian Gerst
2019-11-07 19:54 ` Linus Torvalds
2019-11-07 21:00 ` Brian Gerst
2019-11-07 21:32 ` Thomas Gleixner
2019-11-07 23:20 ` hpa
2019-11-07 21:44 ` Linus Torvalds
2019-11-08 1:12 ` H. Peter Anvin
2019-11-08 2:12 ` Brian Gerst
2019-11-10 17:21 ` Andy Lutomirski
2019-11-06 19:35 ` [patch 6/9] x86/iopl: Fixup misleading comment Thomas Gleixner
2019-11-06 19:35 ` [patch 7/9] x86/iopl: Restrict iopl() permission scope Thomas Gleixner
2019-11-07 9:09 ` Peter Zijlstra
2019-11-10 17:26 ` Andy Lutomirski
2019-11-10 20:31 ` Thomas Gleixner
2019-11-10 21:05 ` Andy Lutomirski
2019-11-10 21:21 ` Thomas Gleixner
2019-11-06 19:35 ` [patch 8/9] x86/iopl: Remove legacy IOPL option Thomas Gleixner
2019-11-07 6:11 ` Jürgen Groß
2019-11-07 6:26 ` hpa
2019-11-07 16:44 ` Stephen Hemminger
2019-11-07 9:13 ` Peter Zijlstra
2019-11-06 19:35 ` [patch 9/9] selftests/x86/iopl: Verify that CLI/STI result in #GP Thomas Gleixner
2019-11-07 7:28 ` [patch] x86/iopl: Remove unused local variable, update comments in ksys_ioperm() Ingo Molnar
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