blob: a5f86c451ba9ed6164014c2c182b5ce60ac28a54 [file] [log] [blame]
From 3e6fcb7bc41cd4b546e1f61174cf380a3d9acada Mon Sep 17 00:00:00 2001
From: Thomas Huth <>
Date: Thu, 29 Aug 2019 14:25:17 +0200
Subject: [PATCH] KVM: s390: Test for bad access register and size at the start
of S390_MEM_OP
commit a13b03bbb4575b350b46090af4dfd30e735aaed1 upstream.
If the KVM_S390_MEM_OP ioctl is called with an access register >= 16,
then there is certainly a bug in the calling userspace application.
We check for wrong access registers, but only if the vCPU was already
in the access register mode before (i.e. the SIE block has recorded
it). The check is also buried somewhere deep in the calling chain (in
the function ar_translation()), so this is somewhat hard to find.
It's better to always report an error to the userspace in case this
field is set wrong, and it's safer in the KVM code if we block wrong
values here early instead of relying on a check somewhere deep down
the calling chain, so let's add another check to kvm_s390_guest_mem_op()
We also should check that the "size" is non-zero here (thanks to Janosch
Frank for the hint!). If we do not check the size, we could call vmalloc()
with this 0 value, and this will cause a kernel warning.
Signed-off-by: Thomas Huth <>
Reviewed-by: Cornelia Huck <>
Reviewed-by: Janosch Frank <>
Reviewed-by: David Hildenbrand <>
Signed-off-by: Christian Borntraeger <>
Signed-off-by: Paul Gortmaker <>
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 4934141689d2..db64187e9505 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4259,7 +4259,7 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION
- if (mop->flags & ~supported_flags)
+ if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size)
return -EINVAL;
if (mop->size > MEM_OP_MAX_SIZE)