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 --- 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; -- 2.55.0