On 03/02/2023 18.48, Sean Christopherson wrote:
On Fri, Feb 03, 2023, Thomas Huth wrote:
kvm_vm_ioctl_get_nr_mmu_pages() tries to return a "unsigned long" value,
but its caller only stores ther return value in an "int" - which is also
what all the other kvm_vm_ioctl_*() functions are returning. So returning
values that do not fit into a 32-bit integer anymore does not work here.
It's better to adjust the return type, add a sanity check and return an
error instead if the value is too big.
Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index da4bbd043a7b..caa2541833dd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6007,8 +6007,11 @@ static int kvm_vm_ioctl_set_nr_mmu_pages(struct kvm *kvm,
return 0;
}
-static unsigned long kvm_vm_ioctl_get_nr_mmu_pages(struct kvm *kvm)
+static int kvm_vm_ioctl_get_nr_mmu_pages(struct kvm *kvm)
{
+ if (kvm->arch.n_max_mmu_pages > INT_MAX)
+ return -EOVERFLOW;
+
return kvm->arch.n_max_mmu_pages;
}
My vote is to skip this patch, skip deprecation, and go straight to deleting
KVM_GET_NR_MMU_PAGES. The ioctl() has never worked[*], and none of the VMMs I
checked use it (QEMU, Google's internal VMM, kvmtool, CrosVM).
I guess I'm living too much in the QEMU world where things need to be
deprecated first before removing them ;-)
But sure, if everybody agrees that removing this directly is fine, too, I
can do this in v2.
Thomas
PS: Has there ever been a discussion about the other deprecated interfaces
in include/uapi/linux/kvm.h ? Most of the stuff there seems to be from 2009
... so maybe it's time now to remove that, too?
