diff options
| author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2013-03-05 13:14:40 +0100 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2013-03-07 16:21:19 -0300 |
| commit | 744b37fb5a63d45e92e590967bae82d8ac62e950 (patch) | |
| tree | bbcc033484c4be327a3574965174f841621f2d63 /arch/s390/kvm | |
| parent | 1a0d74e66405a795bb37a4a23ece50f8d8e5e81e (diff) | |
s390/kvm,gaccess: fix guest access return code handling
Guest access functions like copy_to/from_guest() call __guestaddr_to_user()
which in turn call gmap_fault() in order to translate a guest address to a
user space address.
In error case __guest_addr_to_user() returns either -EFAULT or -ENOMEM.
The copy_to/from_guest functions just pass these return values down to the
callers.
The -ENOMEM case however is problematic since there are several places
which access guest memory like:
rc = copy_to_guest(...);
if (rc == -EFAULT)
error_handling();
So in case of -ENOMEM the code assumes that the guest memory access
succeeded even though it failed.
This can cause guest data or state corruption.
If __guestaddr_to_user() returns -ENOMEM the meaning is that a valid user
space mapping exists, but there was not enough memory available when trying
to build the guest mapping. In other words an out-of-memory situation
occured.
For normal user space accesses an out-of-memory situation causes the page
fault handler to map -ENOMEM to -EFAULT (see fixup code in do_no_context()).
We need to do exactly the same for the kvm gaccess functions.
So __guestaddr_to_user() should just map all error codes to -EFAULT.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch/s390/kvm')
| -rw-r--r-- | arch/s390/kvm/gaccess.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h index 4703f129e95e..84d01dd7a8e4 100644 --- a/arch/s390/kvm/gaccess.h +++ b/arch/s390/kvm/gaccess.h @@ -22,13 +22,16 @@ static inline void __user *__guestaddr_to_user(struct kvm_vcpu *vcpu, unsigned long guestaddr) { unsigned long prefix = vcpu->arch.sie_block->prefix; + unsigned long uaddress; if (guestaddr < 2 * PAGE_SIZE) guestaddr += prefix; else if ((guestaddr >= prefix) && (guestaddr < prefix + 2 * PAGE_SIZE)) guestaddr -= prefix; - - return (void __user *) gmap_fault(guestaddr, vcpu->arch.gmap); + uaddress = gmap_fault(guestaddr, vcpu->arch.gmap); + if (IS_ERR_VALUE(uaddress)) + uaddress = -EFAULT; + return (void __user *)uaddress; } static inline int get_guest_u64(struct kvm_vcpu *vcpu, unsigned long guestaddr, |