Re: [PATCH v2 8/9] KVM: s390: Fix potential tiny kernel stack leak

[Christoph Schlameuss]

On Wed Aug 12, 2026 at 12:44 PM CEST, Claudio Imbrenda wrote:
> In some circumstances, one bit of kernel stack could have been leaked
> from dat_cond_set_storage_key().
>
> Fix by clearing prev before use.
>
> Fixes: 8e03e8316eb2 ("KVM: s390: KVM page table management functions: storage keys")
> Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>

Reviewed-by: Christoph Schlameuss <schlameuss@xxxxxxxxxxxxx>

> ---
>  arch/s390/kvm/dat.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/s390/kvm/dat.c b/arch/s390/kvm/dat.c
> index f4dd6f783417..f2ea013cb33e 100644
> --- a/arch/s390/kvm/dat.c
> +++ b/arch/s390/kvm/dat.c
> @@ -737,6 +737,7 @@ int dat_cond_set_storage_key(struct kvm_s390_mmu_cache *mmc, union asce asce, gf
>  	pgste.fp = skey.fp;
>  	pgste.gc = skey.c;
>  	pgste.gr = skey.r;
> +	prev.skey = 0;
>  
>  	if (!ptep->h.i) {
>  		rc = page_cond_set_storage_key(pte_origin(*ptep), skey, &prev, nq, mr, mc);