linux-stable.git/arch/s390/include/asm/pgalloc.h, branch linux-4.4.y

s390/mm: fix asce_bits handling with dynamic pagetable levels

2016-05-19T00:06:44+00:00

commit 723cacbd9dc79582e562c123a0bacf8bfc69e72a upstream.

There is a race with multi-threaded applications between context switch and
pagetable upgrade. In switch_mm() a new user_asce is built from mm->pgd and
mm->context.asce_bits, w/o holding any locks. A concurrent mmap with a
pagetable upgrade on another thread in crst_table_upgrade() could already
have set new asce_bits, but not yet the new mm->pgd. This would result in a
corrupt user_asce in switch_mm(), and eventually in a kernel panic from a
translation exception.

Fix this by storing the complete asce instead of just the asce_bits, which
can then be read atomically from switch_mm(), so that it either sees the
old value or the new value, but no mixture. Both cases are OK. Having the
old value would result in a page fault on access to the higher level memory,
but the fault handler would see the new mm->pgd, if it was a valid access
after the mmap on the other thread has completed. So as worst-case scenario
we would have a page fault loop for the racing thread until the next time
slice.

Also remove dead code and simplify the upgrade/downgrade path, there are no
upgrades from 2 levels, and only downgrades from 3 levels for compat tasks.
There are also no concurrent upgrades, because the mmap_sem is held with
down_write() in do_mmap, so the flush and table checks during upgrade can
be removed.

Reported-by: Michael Munday 
Reviewed-by: Martin Schwidefsky 
Signed-off-by: Gerald Schaefer 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

s390/mm: four page table levels vs. fork

2016-03-16T15:42:58+00:00

commit 3446c13b268af86391d06611327006b059b8bab1 upstream.

The fork of a process with four page table levels is broken since
git commit 6252d702c5311ce9 "[S390] dynamic page tables."

All new mm contexts are created with three page table levels and
an asce limit of 4TB. If the parent has four levels dup_mmap will
add vmas to the new context which are outside of the asce limit.
The subsequent call to copy_page_range will walk the three level
page table structure of the new process with non-zero pgd and pud
indexes. This leads to memory clobbers as the pgd_index *and* the
pud_index is added to the mm->pgd pointer without a pgd_deref
in between.

The init_new_context() function is selecting the number of page
table levels for a new context. The function is used by mm_init()
which in turn is called by dup_mm() and mm_alloc(). These two are
used by fork() and exec(). The init_new_context() function can
distinguish the two cases by looking at mm->context.asce_limit,
for fork() the mm struct has been copied and the number of page
table levels may not change. For exec() the mm_alloc() function
set the new mm structure to zero, in this case a three-level page
table is created as the temporary stack space is located at
STACK_TOP_MAX = 4TB.

This fixes CVE-2016-2143.

Reported-by: Marcin Kościelnicki 
Reviewed-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

s390/kvm: remove delayed reallocation of page tables for KVM

2015-04-23T14:55:49+00:00

Replacing a 2K page table with a 4K page table while a VMA is active
for the affected memory region is fundamentally broken. Rip out the
page table reallocation code and replace it with a simple system
control 'vm.allocate_pgste'. If the system control is set the page
tables for all processes are allocated as full 4K pages, even for
processes that do not need it.

Signed-off-by: Martin Schwidefsky

s390: remove 31 bit support

2015-03-25T10:49:33+00:00

Remove the 31 bit support in order to reduce maintenance cost and
effectively remove dead code. Since a couple of years there is no
distribution left that comes with a 31 bit kernel.

The 31 bit kernel also has been broken since more than a year before
anybody noticed. In addition I added a removal warning to the kernel
shown at ipl for 5 minutes: a960062e5826 ("s390: add 31 bit warning
message") which let everybody know about the plan to remove 31 bit
code. We didn't get any response.

Given that the last 31 bit only machine was introduced in 1999 let's
remove the code.
Anybody with 31 bit user space code can still use the compat mode.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2014-12-19T00:05:28+00:00

Pull KVM update from Paolo Bonzini:
 "3.19 changes for KVM:

   - spring cleaning: removed support for IA64, and for hardware-
     assisted virtualization on the PPC970

   - ARM, PPC, s390 all had only small fixes

  For x86:
   - small performance improvements (though only on weird guests)
   - usual round of hardware-compliancy fixes from Nadav
   - APICv fixes
   - XSAVES support for hosts and guests.  XSAVES hosts were broken
     because the (non-KVM) XSAVES patches inadvertently changed the KVM
     userspace ABI whenever XSAVES was enabled; hence, this part is
     going to stable.  Guest support is just a matter of exposing the
     feature and CPUID leaves support"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (179 commits)
  KVM: move APIC types to arch/x86/
  KVM: PPC: Book3S: Enable in-kernel XICS emulation by default
  KVM: PPC: Book3S HV: Improve H_CONFER implementation
  KVM: PPC: Book3S HV: Fix endianness of instruction obtained from HEIR register
  KVM: PPC: Book3S HV: Remove code for PPC970 processors
  KVM: PPC: Book3S HV: Tracepoints for KVM HV guest interactions
  KVM: PPC: Book3S HV: Simplify locking around stolen time calculations
  arch: powerpc: kvm: book3s_paired_singles.c: Remove unused function
  arch: powerpc: kvm: book3s_pr.c: Remove unused function
  arch: powerpc: kvm: book3s.c: Remove some unused functions
  arch: powerpc: kvm: book3s_32_mmu.c: Remove unused function
  KVM: PPC: Book3S HV: Check wait conditions before sleeping in kvmppc_vcore_blocked
  KVM: PPC: Book3S HV: ptes are big endian
  KVM: PPC: Book3S HV: Fix inaccuracies in ICP emulation for H_IPI
  KVM: PPC: Book3S HV: Fix KSM memory corruption
  KVM: PPC: Book3S HV: Fix an issue where guest is paused on receiving HMI
  KVM: PPC: Book3S HV: Fix computation of tlbie operand
  KVM: PPC: Book3S HV: Add missing HPTE unlock
  KVM: PPC: BookE: Improve irq inject tracepoint
  arm/arm64: KVM: Require in-kernel vgic for the arch timers
  ...

KVM: S390: Create helper function get_guest_storage_key

2014-11-28T12:58:48+00:00

Define get_guest_storage_key which can be used to get the value of a guest
storage key. This compliments the functionality provided by the helper function
set_guest_storage_key. Both functions are needed for live migration of s390
guests that use storage keys.

Signed-off-by: Jason J. Herne 
Reviewed-by: David Hildenbrand 
Signed-off-by: Christian Borntraeger

s390/mm: recfactor global pgste updates

2014-10-27T12:27:23+00:00

Replace the s390 specific page table walker for the pgste updates
with a call to the common code walk_page_range function.
There are now two pte modification functions, one for the reset
of the CMMA state and another one for the initialization of the
storage keys.

Signed-off-by: Dominik Dingel 
Signed-off-by: Martin Schwidefsky

KVM: s390/mm: use radix trees for guest to host mappings

2014-08-26T08:09:02+00:00

Store the target address for the gmap segments in a radix tree
instead of using invalid segment table entries. gmap_translate
becomes a simple radix_tree_lookup, gmap_fault is split into the
address translation with gmap_translate and the part that does
the linking of the gmap shadow page table with the process page
table.
A second radix tree is used to keep the pointers to the segment
table entries for segments that are mapped in the guest address
space. On unmap of a segment the pointer is retrieved from the
radix tree and is used to carry out the segment invalidation in
the gmap shadow page table. As the radix tree can only store one
pointer, each host segment may only be mapped to exactly one
guest location.

Signed-off-by: Martin Schwidefsky 
Signed-off-by: Christian Borntraeger

KVM: s390: Clear storage keys

2014-04-22T07:36:24+00:00

page_table_reset_pgste() already does a complete page table walk to
reset the pgste. Enhance it to initialize the storage keys to
PAGE_DEFAULT_KEY if requested by the caller. This will be used
for lazy storage key handling. Also provide an empty stub for
!CONFIG_PGSTE

Lets adopt the current code (diag 308) to not clear the keys.

Signed-off-by: Dominik Dingel 
Acked-by: Martin Schwidefsky 
Signed-off-by: Christian Borntraeger

s390/mm: enable split page table lock for PMD level

2014-02-21T07:50:22+00:00

Add the pgtable_pmd_page_ctor/pgtable_pmd_page_dtor calls to the pmd
allocation and free functions and enable ARCH_ENABLE_SPLIT_PMD_PTLOCK
for 64 bit.

Signed-off-by: Martin Schwidefsky