From: Igor Mammedov imammedo@redhat.com
commit 13a17cc0526f08d1df9507f7484176371cd263a0 upstream.
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: afdad61615cc ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/s390/kvm/kvm-s390.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1013,6 +1013,8 @@ static int kvm_s390_vm_start_migration(s /* 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