CC Konstantin,
I hope you can find the right people. Looks that my (and Janis) emaildid not make it to linux-s390 and kvm at vger lists.
Message-ID: <6ea27647-fbbe-3962-03a0-8ca5340fc7fd@xxxxxxxxxxxxx>
Am 09.02.22 um 10:08 schrieb Christian Borntraeger:
Am 09.02.22 um 09:49 schrieb Janis Schoetterl-Glausch:
On 2/9/22 08:34, Christian Borntraeger wrote:
Am 07.02.22 um 17:59 schrieb Janis Schoetterl-Glausch:
User space needs a mechanism to perform key checked accesses when
emulating instructions.
The key can be passed as an additional argument.
Having an additional argument is flexible, as user space can
pass the guest PSW's key, in order to make an access the same way the
CPU would, or pass another key if necessary.
Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx>
Acked-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
---
arch/s390/kvm/kvm-s390.c | 49 +++++++++++++++++++++++++++++++---------
include/uapi/linux/kvm.h | 8 +++++--
2 files changed, 44 insertions(+), 13 deletions(-)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index cf347e1a4f17..71e61fb3f0d9 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -32,6 +32,7 @@
#include <linux/sched/signal.h>
#include <linux/string.h>
#include <linux/pgtable.h>
+#include <linux/bitfield.h>
#include <asm/asm-offsets.h>
#include <asm/lowcore.h>
@@ -2359,6 +2360,11 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
return r;
}
+static bool access_key_invalid(u8 access_key)
+{
+ return access_key > 0xf;
+}
+
long kvm_arch_vm_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
@@ -4687,34 +4693,54 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
struct kvm_s390_mem_op *mop)
{
void __user *uaddr = (void __user *)mop->buf;
+ u8 access_key = 0, ar = 0;
void *tmpbuf = NULL;
+ bool check_reserved;
int r = 0;
const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION
- | KVM_S390_MEMOP_F_CHECK_ONLY;
+ | KVM_S390_MEMOP_F_CHECK_ONLY
+ | KVM_S390_MEMOP_F_SKEY_PROTECTION;
- if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size)
+ if (mop->flags & ~supported_flags || !mop->size)
return -EINVAL;
-
if (mop->size > MEM_OP_MAX_SIZE)
return -E2BIG;
-
if (kvm_s390_pv_cpu_is_protected(vcpu))
return -EINVAL;
-
if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) {
tmpbuf = vmalloc(mop->size);
if (!tmpbuf)
return -ENOMEM;
}
+ ar = mop->ar;
+ mop->ar = 0;
Why this assignment to 0?
It's so the check of reserved below works like that, they're all part of the anonymous union.
Ah, I see. This is ugly :-)
+ if (ar >= NUM_ACRS)
+ return -EINVAL;
+ if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) {
+ access_key = mop->key;
+ mop->key = 0;
and this? I think we can leave mop unchanged.
In fact, why do we add the ar and access_key variable?
This breaks the check from above (if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size)) into two checks
and it will create a memleak for tmpbuf.
I can move the allocation down, goto out or get rid of the reserved check and keep everything as before.
First is simpler, but second makes handling that case more explicit and might help in the future.
Maybe add a reserved_02 field in the anon struct and check this for being zero and get rid of the local variables?
Patch 6 has the same issue in the vm ioctl handler.
Simply use mop->key and mop->ar below and get rid of the local variables.
The structure has no concurrency and gcc will handle that just as the local variable.
Other than that this looks good.
[...]
