From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Stephen Hemminger <stephen@networkplumber.org>,
Willy Tarreau <w@1wt.eu>, Juergen Gross <jgross@suse.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [patch 7/9] x86/iopl: Restrict iopl() permission scope
Date: Sun, 10 Nov 2019 21:31:21 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.21.1911102125110.12583@nanos.tec.linutronix.de> (raw)
In-Reply-To: <a1afc4bb-c90e-db58-42f2-da91a50b1872@kernel.org>
On Sun, 10 Nov 2019, Andy Lutomirski wrote:
> On 11/6/19 11:35 AM, Thomas Gleixner wrote:
> > +
> > + if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION)) {
> > + struct tss_struct *tss;
> > + unsigned int tss_base;
> > +
> > + /* Prevent racing against a task switch */
> > + preempt_disable();
> > + tss = this_cpu_ptr(&cpu_tss_rw);
> > + if (level == 3) {
> > + /* Grant access to all I/O ports */
> > + set_thread_flag(TIF_IO_BITMAP);
> > + tss_base = IO_BITMAP_OFFSET_VALID_ALL;
>
> Where is the actual TSS updated?
Here. It sets the offset to the all zero bitmap. That's all it needs.
> > + } else if (t->io_bitmap_ptr) {
> > + /* Thread has a I/O bitmap */
> > + tss_update_io_bitmap(tss, t);
> > + set_thread_flag(TIF_IO_BITMAP);
> > + tss_base = IO_BITMAP_OFFSET_VALID_MAP;
> > + } else {
> > + /* Take it out of the context switch work burden */
> > + clear_thread_flag(TIF_IO_BITMAP);
> > + tss_base = IO_BITMAP_OFFSET_INVALID;
>
> Ditto.
>
> I think what you need to do is have a single function, called by
> exit_thread(), switch_to(), and here, that updates the TSS to match a
> given task's IO bitmap state. This is probably switch_to_bitmap() or
> similar.
Well, no. exit_thread() and this here actually fiddle with the TIF bit
which is not what the switch to case does. There is some stuff which can be
shared.
> (Maybe it already is, but I swear I checked all the patches in the
> series and I can't find the body of tss_update_io_bitmap(). But you
> should call it in all branches of this if-else thing.)
It's in that very same patch:
> -static void tss_update_io_bitmap(struct tss_struct *tss,
> - struct thread_struct *thread)
> +void tss_update_io_bitmap(struct tss_struct *tss, struct thread_struct *thread)
> {
Let me try to get a bit more reuse. Which still leaves the TIF bit fiddling
in this code path.
Thanks,
tglx
next prev parent reply other threads:[~2019-11-10 20:31 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
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 [this message]
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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