Messages in this thread | | | Date | Thu, 30 Jul 2015 11:53:34 -0400 | From | Boris Ostrovsky <> | Subject | Re: [PATCH v5 0/4] x86: modify_ldt improvement, test, and config option |
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On 07/28/2015 01:29 AM, Andy Lutomirski wrote: > This is intended for x86/urgent. Sorry for taking so long, but it > seemed nice to avoid breaking Xen. > > This fixes the "dazed and confused" issue which was exposed by the > CVE-2015-5157 fix. 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. > > Boris, could I get a Tested-by, assuming this works for you?
As far as Xen guests are concerned,
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
But ldt_gdt_32 test segfaults on 64-bit kernels. Baremetal and virt. I thought it worked for me before but can't reproduce this with older patches. Does it work for you?
-boris
> > Willy and Kees: I left the config option alone. The -tiny people will > like it, and we can always add a sysctl of some sort later. > > Changes from v4: > - Fix Xen even better (patch 1 is new). > - Reorder the patches to make a little more sense. > > Changes from v3: > - Hopefully fixed Xen. > - Fixed 32-bit test case on 32-bit native kernel. > - Fix bogus vumnap for some LDT sizes. > - Strengthen test case to check all LDT sizes (catches bogus vunmap). > - Lots of cleanups, mostly from Borislav. > - Simplify IPI code using on_each_cpu_mask. > > Changes from v2: > - Allocate ldt_struct and the LDT entries separately. This should fix Xen. > - Stop using write_ldt_entry, since I'm pretty sure it's unnecessary now > that we no longer mutate an in-use LDT. (Xen people, can you check?) > > 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 (4): > x86/xen: Unmap aliases in xen_alloc_ldt and xen_free_ldt > x86/ldt: Make modify_ldt synchronous > selftests/x86, x86/ldt: Add a selftest for modify_ldt > x86/ldt: Make modify_ldt optional > > 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 | 68 ++++- > 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 | 262 +++++++++-------- > arch/x86/kernel/process_64.c | 6 +- > arch/x86/kernel/step.c | 8 +- > arch/x86/power/cpu.c | 3 +- > arch/x86/xen/enlighten.c | 12 + > kernel/sys_ni.c | 1 + > tools/testing/selftests/x86/Makefile | 2 +- > tools/testing/selftests/x86/ldt_gdt.c | 520 ++++++++++++++++++++++++++++++++++ > 15 files changed, 787 insertions(+), 155 deletions(-) > create mode 100644 tools/testing/selftests/x86/ldt_gdt.c >
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