From: Toshi Kani <toshi.kani@hpe.com>
To: Stas Sergeev <stsp@list.ru>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Toshi Kani <toshi.kani@hp.com>, Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Brian Gerst <brgerst@gmail.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Stas Sergeev <stsp@users.sourceforge.net>
Subject: Re: [PATCH v2 0/4] x86: sigcontext fixes, again
Date: Wed, 28 Oct 2015 13:22:42 -0600 [thread overview]
Message-ID: <1446060162.20657.136.camel@hpe.com> (raw)
In-Reply-To: <1446050061.20657.106.camel@hpe.com>
On Wed, 2015-10-28 at 10:34 -0600, Toshi Kani wrote:
> On Wed, 2015-10-28 at 12:53 +0300, Stas Sergeev wrote:
> > 28.10.2015 03:04, Toshi Kani пишет:
> > > On Wed, 2015-10-28 at 07:37 +0900, Linus Torvalds wrote:
> > > > On Tue, Oct 27, 2015 at 11:05 PM, Stas Sergeev <stsp@list.ru>
> > > > wrote:
> > > > >
> > > > > I can't easily post an Oops: under X it doesn't even appear -
> > > > > machine freezes immediately, and under non-KMS console it is
> > > > > possible to get one, but difficult to screen-shot (using bare
> > > > > metal, not VM). Also the Oops was seemingly unrelated.
> > > > > And if you run "dosemu -s" under non-KMS console, you'll also
> > > > > reproduce this one:
> > > > > https://bugzilla.kernel.org/show_bug.cgi?id=97321
> > > >
> > > > Hmm. Andrew Morton responded to that initially, but then nothing
> > > > happened, and now it's been another six months. Andrew?
> > > >
> > > > The arch/x86/mm/pat.c error handling does seem to be suspect. This
> > > > is all code several years old, so none of this is new, and I think
> > > > Suresh is gone. Adding a few other people with recent sign-offs to
> > > > that file, in the hope that somebody feels like they own it..
> > >
> > > In the case of PFNMAP, the range should always be mapped. So, I
> > > wonder why follow_phys() failed with the !pte_present() check.
> > >
> > > Stas, do you have a test program that can reproduce 97321?
> > Get dosemu2 from here:
> > https://github.com/stsp/dosemu2/releases
> > or from git, or get dosemu1.
> > Then boot your kernel with "nomodeset=1" to get a text console.
> > Run
> >
> > dosemu -s
> >
> > and you'll get the bug.
I looked at the dosemu code and was able to reproduce the issue with a test
program. This problem happens when mremap() to /dev/mem (or PFNMAP) is
called with MREMAP_FIXED.
In this case, mremap calls move_vma(), which first calls move_page_tables()
to remap the translation and then calls do_munmap() to remove the original
mapping. Hence, when untrack_pfn() is called from do_munmap(), the
original map is already removed, and follow_phys() fails with the
!pte_present() check.
I think there are a couple of issues:
- If track_pfn() ignores an error from follow_phys() and skips
free_pfn_range(), PAT continues to track the original map that is removed.
- track_pfn() calls free_pfn_range() to untrack a given free range.
However, rbt_memtype_erase() requires the free range match exactly to the
tracked range. This does not support mremap, which needs to free up part
of the tracked range.
- PAT does not track a new translation specified by mremap() with MREMAP_F
IXED.
Thanks,
-Toshi
next prev parent reply other threads:[~2015-10-28 19:26 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-26 1:25 [PATCH v2 0/4] x86: sigcontext fixes, again Andy Lutomirski
2015-10-26 1:25 ` [PATCH v2 1/4] x86/signal/64: Add a comment about sigcontext->fs and gs Andy Lutomirski
2015-10-31 15:25 ` Stas Sergeev
2015-12-07 23:23 ` Andy Lutomirski
2015-12-29 12:24 ` Stas Sergeev
2015-12-29 12:31 ` Andy Lutomirski
2015-10-26 1:25 ` [PATCH v2 2/4] x86/signal/64: Fix SS if needed when delivering a 64-bit signal Andy Lutomirski
2015-10-26 1:25 ` [PATCH v2 3/4] x86/signal/64: Re-add support for SS in the 64-bit signal context Andy Lutomirski
2015-10-31 15:18 ` Stas Sergeev
2015-10-26 1:25 ` [PATCH v2 4/4] selftests/x86: Add tests for UC_SIGCONTEXT_SS and UC_STRICT_RESTORE_SS Andy Lutomirski
2015-10-26 11:45 ` [PATCH v2 0/4] x86: sigcontext fixes, again Stas Sergeev
2015-10-27 0:52 ` Andy Lutomirski
2015-10-27 14:05 ` Stas Sergeev
2015-10-27 22:37 ` Linus Torvalds
2015-10-28 0:04 ` Toshi Kani
2015-10-28 9:53 ` Stas Sergeev
2015-10-28 16:34 ` Toshi Kani
2015-10-28 19:22 ` Toshi Kani [this message]
2015-10-28 22:51 ` Toshi Kani
2015-10-31 11:58 ` Stas Sergeev
2015-11-02 17:01 ` Toshi Kani
2015-10-30 23:50 ` Andy Lutomirski
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