lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Fri, 11 Sep 2015 11:15:30 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	gleb@...nel.org, pbonzini@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, cornelia.huck@...ibm.com
Subject: Re: [PATCH V4 0/4] Fast MMIO eventfd fixes

On Fri, Sep 11, 2015 at 11:17:33AM +0800, Jason Wang wrote:
> Hi:
> 
> This series fixes two issues of fast mmio eventfd:
> 
> 1) A single iodev instance were registerd on two buses: KVM_MMIO_BUS
>    and KVM_FAST_MMIO_BUS. This will cause double in
>    ioeventfd_destructor()
> 2) A zero length iodev on KVM_MMIO_BUS will never be found but
>    kvm_io_bus_cmp(). This will lead e.g the eventfd will be trapped by
>    qemu instead of host.
> 
> 1 is fixed by allocating two instances of iodev. 2 is fixed by ignore
> the actual length if the length of iodev is zero in kvm_io_bus_cmp().
> 
> Please review.

I think we should add a capability for fast mmio.
This way, userspace can avoid crashing buggy kernels.

> Changes from V3:
> 
> - Don't do search on two buses when trying to do write on
>   KVM_MMIO_BUS. This fixes a small regression found by vmexit.flat.
> - Since we don't do search on two buses, change kvm_io_bus_cmp() to
>   let it can find zero length iodevs.
> - Fix the unnecessary lines in tracepoint patch.
> 
> Changes from V2:
> - Tweak styles and comment suggested by Cornelia.
> 
> Changes from v1:
> - change ioeventfd_bus_from_flags() to return KVM_FAST_MMIO_BUS when
>   needed to save lots of unnecessary changes.
> 
> Jason Wang (4):
>   kvm: factor out core eventfd assign/deassign logic
>   kvm: fix double free for fast mmio eventfd
>   kvm: fix zero length mmio searching
>   kvm: add tracepoint for fast mmio
> 
>  arch/x86/kvm/trace.h |  18 ++++++++
>  arch/x86/kvm/vmx.c   |   1 +
>  arch/x86/kvm/x86.c   |   1 +
>  virt/kvm/eventfd.c   | 124 ++++++++++++++++++++++++++++++---------------------
>  virt/kvm/kvm_main.c  |   4 +-
>  5 files changed, 96 insertions(+), 52 deletions(-)
> 
> -- 
> 2.1.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists