Patch "KVM: s390: do not expose random data via facility bitmap" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

KVM: s390: do not expose random data via facility bitmap

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-s390-do-not-expose-random-data-via-facility-bitmap.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Christian Borntraeger <[email protected]>
Date: Thu, 12 Jan 2017 16:25:15 +0100
Subject: KVM: s390: do not expose random data via facility bitmap

From: Christian Borntraeger <[email protected]>

commit 04478197416e3a302e9ebc917ba1aa884ef9bfab upstream.

kvm_s390_get_machine() populates the facility bitmap by copying bytes from the host results that are stored in a 256 byte array in the prefix page. The KVM code does use the size of the target buffer (2k), thus copying and exposing unrelated kernel memory (mostly machine check related logout data).

Let's use the size of the source buffer instead. This is ok, as the target buffer will always be greater or equal than the source buffer as the KVM internal buffers (and thus S390_ARCH_FAC_LIST_SIZE_BYTE) cover the maximum possible size that is allowed by STFLE, which is 256 doublewords. All structures are zero allocated so we can leave bytes 256-2047 unchanged.

Add a similar fix for kvm_arch_init_vm().

---
 arch/s390/kvm/kvm-s390.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -916,7 +916,7 @@ static int kvm_s390_get_machine(struct k
 	memcpy(&mach->fac_mask, kvm->arch.model.fac_mask,
 	       S390_ARCH_FAC_LIST_SIZE_BYTE);
 	memcpy((unsigned long *)&mach->fac_list, S390_lowcore.stfle_fac_list,
-	       S390_ARCH_FAC_LIST_SIZE_BYTE);
+	       sizeof(S390_lowcore.stfle_fac_list));
 	if (copy_to_user((void __user *)attr->addr, mach, sizeof(*mach)))
 		ret = -EFAULT;
 	kfree(mach);

@@ -1437,7 +1437,7 @@ int kvm_arch_init_vm(struct kvm *kvm, un
 
 	/* Populate the facility mask initially. */
 	memcpy(kvm->arch.model.fac_mask, S390_lowcore.stfle_fac_list,
-	       S390_ARCH_FAC_LIST_SIZE_BYTE);
+	       sizeof(S390_lowcore.stfle_fac_list));
 	for (i = 0; i < S390_ARCH_FAC_LIST_SIZE_U64; i++) {
 		if (i < kvm_s390_fac_list_mask_size())
 			kvm->arch.model.fac_mask[i] &= kvm_s390_fac_list_mask[i];

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/kvm-s390-do-not-expose-random-data-via-facility-bitmap.patch