KVM: arm64: Restrict EL2 stage-1 changes in protected mode
The host kernel is currently able to change EL2 stage-1 mappings without restrictions thanks to the __pkvm_create_mappings() hypercall. But in a world where the host is no longer part of the TCB, this clearly poses a problem. To fix this, introduce a new hypercall to allow the host to share a physical memory page with the hypervisor, and remove the __pkvm_create_mappings() variant. The new hypercall implements ownership and permission checks before allowing the sharing operation, and it annotates the shared page in the hypervisor stage-1 and host stage-2 page-tables. Signed-off-by: Quentin Perret <qperret@google.com> Reviewed-by: Fuad Tabba <tabba@google.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20210809152448.1810400-21-qperret@google.com
This commit is contained in:
Родитель
f9370010e9
Коммит
66c57edd3b
|
@ -59,7 +59,7 @@
|
|||
#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 13
|
||||
#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 14
|
||||
#define __KVM_HOST_SMCCC_FUNC___pkvm_init 15
|
||||
#define __KVM_HOST_SMCCC_FUNC___pkvm_create_mappings 16
|
||||
#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp 16
|
||||
#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping 17
|
||||
#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 18
|
||||
#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 19
|
||||
|
|
|
@ -49,6 +49,7 @@ extern struct host_kvm host_kvm;
|
|||
extern const u8 pkvm_hyp_id;
|
||||
|
||||
int __pkvm_prot_finalize(void);
|
||||
int __pkvm_host_share_hyp(u64 pfn);
|
||||
|
||||
bool addr_is_memory(phys_addr_t phys);
|
||||
int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);
|
||||
|
|
|
@ -140,14 +140,11 @@ static void handle___pkvm_cpu_set_vector(struct kvm_cpu_context *host_ctxt)
|
|||
cpu_reg(host_ctxt, 1) = pkvm_cpu_set_vector(slot);
|
||||
}
|
||||
|
||||
static void handle___pkvm_create_mappings(struct kvm_cpu_context *host_ctxt)
|
||||
static void handle___pkvm_host_share_hyp(struct kvm_cpu_context *host_ctxt)
|
||||
{
|
||||
DECLARE_REG(unsigned long, start, host_ctxt, 1);
|
||||
DECLARE_REG(unsigned long, size, host_ctxt, 2);
|
||||
DECLARE_REG(unsigned long, phys, host_ctxt, 3);
|
||||
DECLARE_REG(enum kvm_pgtable_prot, prot, host_ctxt, 4);
|
||||
DECLARE_REG(u64, pfn, host_ctxt, 1);
|
||||
|
||||
cpu_reg(host_ctxt, 1) = __pkvm_create_mappings(start, size, phys, prot);
|
||||
cpu_reg(host_ctxt, 1) = __pkvm_host_share_hyp(pfn);
|
||||
}
|
||||
|
||||
static void handle___pkvm_create_private_mapping(struct kvm_cpu_context *host_ctxt)
|
||||
|
@ -185,7 +182,7 @@ static const hcall_t host_hcall[] = {
|
|||
HANDLE_FUNC(__vgic_v3_restore_aprs),
|
||||
HANDLE_FUNC(__pkvm_init),
|
||||
HANDLE_FUNC(__pkvm_cpu_set_vector),
|
||||
HANDLE_FUNC(__pkvm_create_mappings),
|
||||
HANDLE_FUNC(__pkvm_host_share_hyp),
|
||||
HANDLE_FUNC(__pkvm_create_private_mapping),
|
||||
HANDLE_FUNC(__pkvm_prot_finalize),
|
||||
};
|
||||
|
|
|
@ -339,6 +339,94 @@ unlock:
|
|||
return ret;
|
||||
}
|
||||
|
||||
static inline bool check_prot(enum kvm_pgtable_prot prot,
|
||||
enum kvm_pgtable_prot required,
|
||||
enum kvm_pgtable_prot denied)
|
||||
{
|
||||
return (prot & (required | denied)) == required;
|
||||
}
|
||||
|
||||
int __pkvm_host_share_hyp(u64 pfn)
|
||||
{
|
||||
phys_addr_t addr = hyp_pfn_to_phys(pfn);
|
||||
enum kvm_pgtable_prot prot, cur;
|
||||
void *virt = __hyp_va(addr);
|
||||
enum pkvm_page_state state;
|
||||
kvm_pte_t pte;
|
||||
int ret;
|
||||
|
||||
if (!addr_is_memory(addr))
|
||||
return -EINVAL;
|
||||
|
||||
hyp_spin_lock(&host_kvm.lock);
|
||||
hyp_spin_lock(&pkvm_pgd_lock);
|
||||
|
||||
ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, NULL);
|
||||
if (ret)
|
||||
goto unlock;
|
||||
if (!pte)
|
||||
goto map_shared;
|
||||
|
||||
/*
|
||||
* Check attributes in the host stage-2 PTE. We need the page to be:
|
||||
* - mapped RWX as we're sharing memory;
|
||||
* - not borrowed, as that implies absence of ownership.
|
||||
* Otherwise, we can't let it got through
|
||||
*/
|
||||
cur = kvm_pgtable_stage2_pte_prot(pte);
|
||||
prot = pkvm_mkstate(0, PKVM_PAGE_SHARED_BORROWED);
|
||||
if (!check_prot(cur, PKVM_HOST_MEM_PROT, prot)) {
|
||||
ret = -EPERM;
|
||||
goto unlock;
|
||||
}
|
||||
|
||||
state = pkvm_getstate(cur);
|
||||
if (state == PKVM_PAGE_OWNED)
|
||||
goto map_shared;
|
||||
|
||||
/*
|
||||
* Tolerate double-sharing the same page, but this requires
|
||||
* cross-checking the hypervisor stage-1.
|
||||
*/
|
||||
if (state != PKVM_PAGE_SHARED_OWNED) {
|
||||
ret = -EPERM;
|
||||
goto unlock;
|
||||
}
|
||||
|
||||
ret = kvm_pgtable_get_leaf(&pkvm_pgtable, (u64)virt, &pte, NULL);
|
||||
if (ret)
|
||||
goto unlock;
|
||||
|
||||
/*
|
||||
* If the page has been shared with the hypervisor, it must be
|
||||
* already mapped as SHARED_BORROWED in its stage-1.
|
||||
*/
|
||||
cur = kvm_pgtable_hyp_pte_prot(pte);
|
||||
prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
|
||||
if (!check_prot(cur, prot, ~prot))
|
||||
ret = EPERM;
|
||||
goto unlock;
|
||||
|
||||
map_shared:
|
||||
/*
|
||||
* If the page is not yet shared, adjust mappings in both page-tables
|
||||
* while both locks are held.
|
||||
*/
|
||||
prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
|
||||
ret = pkvm_create_mappings_locked(virt, virt + PAGE_SIZE, prot);
|
||||
BUG_ON(ret);
|
||||
|
||||
prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_OWNED);
|
||||
ret = host_stage2_idmap_locked(addr, PAGE_SIZE, prot);
|
||||
BUG_ON(ret);
|
||||
|
||||
unlock:
|
||||
hyp_spin_unlock(&pkvm_pgd_lock);
|
||||
hyp_spin_unlock(&host_kvm.lock);
|
||||
|
||||
return ret;
|
||||
}
|
||||
|
||||
void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
|
||||
{
|
||||
struct kvm_vcpu_fault_info fault;
|
||||
|
|
|
@ -259,10 +259,8 @@ static int __create_hyp_mappings(unsigned long start, unsigned long size,
|
|||
{
|
||||
int err;
|
||||
|
||||
if (!kvm_host_owns_hyp_mappings()) {
|
||||
return kvm_call_hyp_nvhe(__pkvm_create_mappings,
|
||||
start, size, phys, prot);
|
||||
}
|
||||
if (WARN_ON(!kvm_host_owns_hyp_mappings()))
|
||||
return -EINVAL;
|
||||
|
||||
mutex_lock(&kvm_hyp_pgd_mutex);
|
||||
err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot);
|
||||
|
@ -282,6 +280,21 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
|
|||
}
|
||||
}
|
||||
|
||||
static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end)
|
||||
{
|
||||
phys_addr_t addr;
|
||||
int ret;
|
||||
|
||||
for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) {
|
||||
ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp,
|
||||
__phys_to_pfn(addr));
|
||||
if (ret)
|
||||
return ret;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/**
|
||||
* create_hyp_mappings - duplicate a kernel virtual address range in Hyp mode
|
||||
* @from: The virtual kernel start address of the range
|
||||
|
@ -302,6 +315,13 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
|
|||
if (is_kernel_in_hyp_mode())
|
||||
return 0;
|
||||
|
||||
if (!kvm_host_owns_hyp_mappings()) {
|
||||
if (WARN_ON(prot != PAGE_HYP))
|
||||
return -EPERM;
|
||||
return pkvm_share_hyp(kvm_kaddr_to_phys(from),
|
||||
kvm_kaddr_to_phys(to));
|
||||
}
|
||||
|
||||
start = start & PAGE_MASK;
|
||||
end = PAGE_ALIGN(end);
|
||||
|
||||
|
|
Загрузка…
Ссылка в новой задаче