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KVM: s390: kvm_s390_vm_start_migration: check dirty_bitmap before using it as target for memset()

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If userspace doesn't set KVM_MEM_LOG_DIRTY_PAGES on memslot before calling
kvm_s390_vm_start_migration(), kernel will oops with:

  Unable to handle kernel pointer dereference in virtual kernel address space
  Failing address: 0000000000000000 TEID: 0000000000000483
  Fault in home space mode while using kernel ASCE.
  AS:0000000002a2000b R2:00000001bff8c00b R3:00000001bff88007 S:00000001bff91000 P:000000000000003d
  Oops: 0004 ilc:2 [#1] SMP
  ...
  Call Trace:
  ([<001fffff804ec552>] kvm_s390_vm_set_attr+0x347a/0x3828 [kvm])
   [<001fffff804ecfc0>] kvm_arch_vm_ioctl+0x6c0/0x1998 [kvm]
   [<001fffff804b67e4>] kvm_vm_ioctl+0x51c/0x11a8 [kvm]
   [<00000000008ba572>] do_vfs_ioctl+0x1d2/0xe58
   [<00000000008bb284>] ksys_ioctl+0x8c/0xb8
   [<00000000008bb2e2>] sys_ioctl+0x32/0x40
   [<000000000175552c>] system_call+0x2b8/0x2d8
  INFO: lockdep is turned off.
  Last Breaking-Event-Address:
   [<0000000000dbaf60>] __memset+0xc/0xa0

due to ms->dirty_bitmap being NULL, which might crash the host.

Make sure that ms->dirty_bitmap is set before using it or
return -EINVAL otherwise.

Cc: <stable@vger.kernel.org>
Fixes: afdad61615 ("KVM: s390: Fix storage attributes migration with memory slots")
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Link: https://lore.kernel.org/kvm/20190911075218.29153-1-imammedo@redhat.com/
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
Igor Mammedov 2019-09-11 03:52:18 -04:00 committed by Christian Borntraeger
parent 609488bc97
commit 13a17cc052
1 changed files with 2 additions and 0 deletions
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2
arch/s390/kvm/kvm-s390.c
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@ -1018,6 +1018,8 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm)
/* mark all the pages in active slots as dirty */
for (slotnr = 0; slotnr < slots->used_slots; slotnr++) {
ms = slots->memslots + slotnr;
if (!ms->dirty_bitmap)
return -EINVAL;
/*
* The second half of the bitmap is only used on x86,
* and would be wasted otherwise, so we put it to good