Re: [PATCH v1 01/11] KVM: s390: Properly handle NULL pointer in dat_cond_set_storage_key()

[Christian Borntraeger <borntraeger@de.ibm.com>]

Am 11.08.26 um 17:56 schrieb Claudio Imbrenda:
> Some callers pass NULL as oldkey. Calling page_cond_set_storage_key()
> will cause that NULL pointer to get dereferenced.
> 
> Fix by checking for NULL and assigning the pointer to a dummy local
> variable to avoid crashes.
> 
> Fixes: 8e03e8316eb2 ("KVM: s390: KVM page table management functions: storage keys")
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

the whole thing looks a bit complicated, but as as fix I cannot see anything better

Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>



> ---
>   arch/s390/kvm/dat.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kvm/dat.c b/arch/s390/kvm/dat.c
> index 3f2d6e8902d7..165c704fcf29 100644
> --- a/arch/s390/kvm/dat.c
> +++ b/arch/s390/kvm/dat.c
> @@ -722,9 +722,12 @@ int dat_cond_set_storage_key(struct kvm_s390_mmu_cache *mmc, union asce asce, gf
>   	if (rc)
>   		return rc;
>   
> -	if (!ptep)
> +	if (!ptep) {
> +		if (!oldkey)
> +			oldkey = &prev;
>   		return page_cond_set_storage_key(large_crste_to_phys(*crstep, gfn), skey, oldkey,
>   						 nq, mr, mc);
> +	}
>   
>   	old = pgste_get_lock(ptep);
>   	pgste = old;