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Groups > linux.kernel > #1217705
| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') |
| Date | 2015-09-02 17:40 +0200 |
| Message-ID | <q4iiK-JG-9@gated-at.bofh.it> (permalink) |
| References | <q4cGm-17b-15@gated-at.bofh.it> <q4gTD-7hJ-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Wed, Sep 2, 2015 at 7:08 AM, Andy Lutomirski <luto@amacapital.net> wrote: > On Sep 2, 2015 2:51 AM, "Stas Sergeev" <stsp@list.ru> wrote: >> >> https://lkml.org/lkml/2015/7/21/208 >> >> Guys, you gonna be kidding. >> Is this a new trend of breaking dosemu, or what? >> >>> VM86 is entirely broken if ptrace, syscall auditing, or >>> NOHZ_FULL is in use. The code is a big undocumented mess, it's >>> a real PITA to test, and it looks like a big chunk of vm86_32.c >> >> >> It is a CPU feature that kernel should support, and always >> did without any problems. If it started to have problems because >> of your actions, then you can as well fix your code. >> >> > No one should be using it anyway. Use DOSBOX or KVM instead. >> >> Have you done the benchmarks between dosbox and dosemu >> before saying that? Please do, thanks. (don't forget to include >> dosemu2 in your benchmarks too, as it outperforms both) > > I wasn't aware of your dosemu variant at the time, and I incorrectly > thought that dosemu was unmaintained. > > Does real mode performance matter any more? > >> >>> Let's accelerate its slow death. >> >> > > Dosemu is much less dead than I thought it was when I wrote that > patch. Sorry :( > >> >> > + Enabling this option adds considerable attack surface to the >> > + kernel and slows down system calls and exception handling. >> >> Yes, I realize that threatening people with the "considerable attack surface" >> is a good way to "accelerate its slow death", but please care to explain >> that attack surface, thankyou. > > The user_mode vs user_mode_vm thing was scary and contained at least > one real bug. That particular issue is gone now, though. > > Before Brian's cleanups, vm86 did horrible things to the entry asm, > the stack layout, and signal handling, and that scared me. That's > hopefully in much better shape now, though. > > The mark_screen_rdonly thing is still kind of scary. It changes PTEs > on arbitrary mappings behind the vm's back. > > I'd be amenable to switching the default back to y and perhaps adding > a sysctl to make the distros more comfortable. Ingo, Kees, Brian, > what do you think? Yeah, I think putting this under distro control (and user control) is the best option here. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 11:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-02 16:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Kees Cook <keescook@chromium.org> - 2015-09-02 17:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 19:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 19:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 20:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 22:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 22:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-02 23:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 23:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 23:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-02 23:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 23:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-03 14:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 14:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-03 17:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 18:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-03 21:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 23:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Chuck Ebbert <cebbert.lkml@gmail.com> - 2015-09-04 12:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 12:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-04 14:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 15:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-04 22:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 23:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 23:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Raymond Jennings <shentino@gmail.com> - 2015-09-05 00:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-05 01:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 00:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-03 19:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-03 19:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 19:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 19:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 19:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 14:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-03 14:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Kees Cook <keescook@chromium.org> - 2015-09-02 20:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 22:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-02 20:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 22:30 +0200
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