diff options
| author | David Hildenbrand <dahi@linux.vnet.ibm.com> | 2015-10-26 08:41:29 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-12-09 14:31:19 -0500 |
| commit | 8003ebad9780e21a3b89f62876fb341890adf2f7 (patch) | |
| tree | a9cb62e44f037c2b3697e6ba63db0333d5c4308f | |
| parent | fb4e563b399e9b1ddca1e4ccdbd2947d51fe780d (diff) | |
KVM: s390: SCA must not cross page boundaries
commit c5c2c393468576bad6d10b2b5fefff8cd25df3f4 upstream.
We seemed to have missed a few corner cases in commit f6c137ff00a4
("KVM: s390: randomize sca address").
The SCA has a maximum size of 2112 bytes. By setting the sca_offset to
some unlucky numbers, we exceed the page.
0x7c0 (1984) -> Fits exactly
0x7d0 (2000) -> 16 bytes out
0x7e0 (2016) -> 32 bytes out
0x7f0 (2032) -> 48 bytes out
One VCPU entry is 32 bytes long.
For the last two cases, we actually write data to the other page.
1. The address of the VCPU.
2. Injection/delivery/clearing of SIGP externall calls via SIGP IF.
Especially the 2. happens regularly. So this could produce two problems:
1. The guest losing/getting external calls.
2. Random memory overwrites in the host.
So this problem happens on every 127 + 128 created VM with 64 VCPUs.
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/s390/kvm/kvm-s390.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index f32f843a3631..e6729459fdb3 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1037,7 +1037,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) if (!kvm->arch.sca) goto out_err; spin_lock(&kvm_lock); - sca_offset = (sca_offset + 16) & 0x7f0; + sca_offset += 16; + if (sca_offset + sizeof(struct sca_block) > PAGE_SIZE) + sca_offset = 0; kvm->arch.sca = (struct sca_block *) ((char *) kvm->arch.sca + sca_offset); spin_unlock(&kvm_lock); |