KVM: s390: SCA must not cross page boundaries
commit c5c2c393 upstream. We seemed to have missed a few corner cases in commit f6c137ff ("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>
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