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

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org> know about it.


>From 04478197416e3a302e9ebc917ba1aa884ef9bfab Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Thu, 12 Jan 2017 16:25:15 +0100
Subject: KVM: s390: do not expose random data via facility bitmap

From: Christian Borntraeger <borntraeger@de.ibm.com>

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().

Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
[found with smatch]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -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 borntraeger@de.ibm.com are

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