linux-kernel - [PATCH v2 0/3] x86: modify_ldt improvement, test, and config option

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Date:	Tue, 21 Jul 2015 12:59:28 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>
Cc:	"security@...nel.org" <security@...nel.org>,
	X86 ML <x86@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Sasha Levin <sasha.levin@...cle.com>,
	linux-kernel@...r.kernel.org,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v2 0/3] x86: modify_ldt improvement, test, and config option

Here's v2.  It fixes the "dazed and confused" issue, I hope.  It's also
probably a good general attack surface reduction, and it replaces some
scary code with IMO less scary code.

Also, servers and embedded systems should probably turn off modify_ldt.
This makes that possible.

Xen people, can you take a look at this?  I think that, with this change,
write_ldt_entry is unnecessary.

Changes from v1:
 - The config option is new.
 - The test case is new.
 - Fixed a missing allocation failure check.
 - Fixed a use-after-free on fork().

Andy Lutomirski (3):
  x86/ldt: Make modify_ldt synchronous
  x86/ldt: Make modify_ldt optional
  selftests/x86, x86/ldt: Add a selftest for modify_ldt

 arch/x86/Kconfig                      |  17 ++
 arch/x86/include/asm/desc.h           |  15 --
 arch/x86/include/asm/mmu.h            |   5 +-
 arch/x86/include/asm/mmu_context.h    |  63 ++++-
 arch/x86/kernel/Makefile              |   3 +-
 arch/x86/kernel/cpu/common.c          |   4 +-
 arch/x86/kernel/cpu/perf_event.c      |  16 +-
 arch/x86/kernel/ldt.c                 | 247 +++++++++--------
 arch/x86/kernel/process_64.c          |   6 +-
 arch/x86/kernel/step.c                |   8 +-
 arch/x86/power/cpu.c                  |   3 +-
 kernel/sys_ni.c                       |   1 +
 tools/testing/selftests/x86/Makefile  |   2 +-
 tools/testing/selftests/x86/ldt_gdt.c | 492 ++++++++++++++++++++++++++++++++++
 14 files changed, 730 insertions(+), 152 deletions(-)
 create mode 100644 tools/testing/selftests/x86/ldt_gdt.c

-- 
2.4.3

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