Patch "kvm: s390: Reject memory region operations for ucontrol VMs" has been added to the 6.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    kvm: s390: Reject memory region operations for ucontrol VMs

to the 6.10-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-reject-memory-region-operations-for-ucontro.patch
and it can be found in the queue-6.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b3ed3d9e756b0014daa962a273240a1f5c7e8746
Author: Christoph Schlameuss <schlameuss@xxxxxxxxxxxxx>
Date:   Mon Jun 24 11:59:02 2024 +0200

    kvm: s390: Reject memory region operations for ucontrol VMs
    
    [ Upstream commit 7816e58967d0e6cadce05c8540b47ed027dc2499 ]
    
    This change rejects the KVM_SET_USER_MEMORY_REGION and
    KVM_SET_USER_MEMORY_REGION2 ioctls when called on a ucontrol VM.
    This is necessary since ucontrol VMs have kvm->arch.gmap set to 0 and
    would thus result in a null pointer dereference further in.
    Memory management needs to be performed in userspace and using the
    ioctls KVM_S390_UCAS_MAP and KVM_S390_UCAS_UNMAP.
    
    Also improve s390 specific documentation for KVM_SET_USER_MEMORY_REGION
    and KVM_SET_USER_MEMORY_REGION2.
    
    Signed-off-by: Christoph Schlameuss <schlameuss@xxxxxxxxxxxxx>
    Fixes: 27e0393f15fc ("KVM: s390: ucontrol: per vcpu address spaces")
    Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240624095902.29375-1-schlameuss@xxxxxxxxxxxxx
    Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
    [frankja@xxxxxxxxxxxxx: commit message spelling fix, subject prefix fix]
    Message-ID: <20240624095902.29375-1-schlameuss@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index a71d91978d9ef..eec8df1dde06a 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1403,6 +1403,12 @@ Instead, an abort (data abort if the cause of the page-table update
 was a load or a store, instruction abort if it was an instruction
 fetch) is injected in the guest.
 
+S390:
+^^^^^
+
+Returns -EINVAL if the VM has the KVM_VM_S390_UCONTROL flag set.
+Returns -EINVAL if called on a protected VM.
+
 4.36 KVM_SET_TSS_ADDR
 ---------------------
 
@@ -6273,6 +6279,12 @@ state.  At VM creation time, all memory is shared, i.e. the PRIVATE attribute
 is '0' for all gfns.  Userspace can control whether memory is shared/private by
 toggling KVM_MEMORY_ATTRIBUTE_PRIVATE via KVM_SET_MEMORY_ATTRIBUTES as needed.
 
+S390:
+^^^^^
+
+Returns -EINVAL if the VM has the KVM_VM_S390_UCONTROL flag set.
+Returns -EINVAL if called on a protected VM.
+
 4.141 KVM_SET_MEMORY_ATTRIBUTES
 -------------------------------
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 54b5b2565df8d..4a74effe68704 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5749,6 +5749,9 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 {
 	gpa_t size;
 
+	if (kvm_is_ucontrol(kvm))
+		return -EINVAL;
+
 	/* When we are protected, we should not change the memory slots */
 	if (kvm_s390_pv_get_handle(kvm))
 		return -EINVAL;