From: Heiko Carstens Date: Tue, 5 Mar 2013 12:14:40 +0000 (+0100) Subject: s390/kvm,gaccess: fix guest access return code handling X-Git-Tag: upstream/snapshot3+hdmi~5185^2~116 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=744b37fb5a63d45e92e590967bae82d8ac62e950;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git 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 Reviewed-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky Signed-off-by: Christian Borntraeger Signed-off-by: Marcelo Tosatti --- diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h index 4703f12..84d01dd 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,