On 19.07.14 09:59, Paul Mackerras wrote:
At present, kvmppc_ld calls kvmppc_xlate, and if kvmppc_xlate returns
any error indication, it returns -ENOENT, which is taken to mean an
HPTE not found error. However, the error could have been a segment
found (no SLB entry) or a permission error. Similarly,
kvmppc_pte_to_hva currently does permission checking, but any error
from it is taken by kvmppc_ld to mean that the access is an emulated
MMIO access. Also, kvmppc_ld does no execute permission checking.
This fixes these problems by (a) returning any error from kvmppc_xlate
directly, (b) moving the permission check from kvmppc_pte_to_hva
into kvmppc_ld, and (c) adding an execute permission check to kvmppc_ld.
This is similar to what was done for kvmppc_st() by commit 82ff911317c3
("KVM: PPC: Deflect page write faults properly in kvmppc_st").
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx>
---
arch/powerpc/kvm/book3s.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 31facfc..087f8f9 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -413,17 +413,10 @@ static hva_t kvmppc_bad_hva(void)
return PAGE_OFFSET;
}
-static hva_t kvmppc_pte_to_hva(struct kvm_vcpu *vcpu, struct kvmppc_pte *pte,
- bool read)
+static hva_t kvmppc_pte_to_hva(struct kvm_vcpu *vcpu, struct kvmppc_pte *pte)
{
hva_t hpage;
- if (read && !pte->may_read)
- goto err;
-
- if (!read && !pte->may_write)
- goto err;
-
hpage = gfn_to_hva(vcpu->kvm, pte->raddr >> PAGE_SHIFT);
if (kvm_is_error_hva(hpage))
goto err;
@@ -462,15 +455,23 @@ int kvmppc_ld(struct kvm_vcpu *vcpu, ulong *eaddr, int size, void *ptr,
{
struct kvmppc_pte pte;
hva_t hva = *eaddr;
+ int rc;
vcpu->stat.ld++;
- if (kvmppc_xlate(vcpu, *eaddr, data, false, &pte))
- goto nopte;
+ rc = kvmppc_xlate(vcpu, *eaddr, data, false, &pte);
+ if (rc)
+ return rc;
*eaddr = pte.raddr;
- hva = kvmppc_pte_to_hva(vcpu, &pte, true);
+ if (!pte.may_read)
+ return -EPERM;
+
+ if (!data && !pte.may_execute)
+ return -ENOEXEC;
We should probably do a full audit of all that code and decide who is
responsible for returning errors where. IIRC our MMU frontends already
check pte.may* and return error codes respectively.
However, double-checking doesn't hurt for now, so I've applied this
patch regardless.
Alex
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