From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: [PATCH v4] drivers/vfio: Fix a redundant copy bug Date: Mon, 29 Oct 2018 15:32:34 -0600 Message-ID: <20181029153234.36e67a6f@t450s.home> References: <1539803924-3190-1-git-send-email-wang6495@umn.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Kangjie Lu , kvm@vger.kernel.org, open list , , David Gibson To: Wenwen Wang Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Mon, 29 Oct 2018 13:56:54 -0500 Wenwen Wang wrote: > Hello, > > Could you please apply this patch? Thanks! I'd like to see testing and/or review from David or Alexey since I also don't have an environment for spapr/eeh. We're already late into the v4.20 merge window so this is probably v4.21 material. Thanks, Alex > On Wed, Oct 17, 2018 at 2:18 PM Wenwen Wang wrote: > > > > In vfio_spapr_iommu_eeh_ioctl(), if the ioctl command is VFIO_EEH_PE_OP, > > the user-space buffer 'arg' is copied to the kernel object 'op' and the > > 'argsz' and 'flags' fields of 'op' are checked. If the check fails, an > > error code EINVAL is returned. Otherwise, 'op.op' is further checked > > through a switch statement to invoke related handlers. If 'op.op' is > > VFIO_EEH_PE_INJECT_ERR, the whole user-space buffer 'arg' is copied again > > to 'op' to obtain the err information. However, in the following execution > > of this case, the fields of 'op', except the field 'err', are actually not > > used. That is, the second copy has a redundant part. Therefore, for > > performance consideration, the redundant part of the second copy should be > > removed. > > > > This patch removes such a part in the second copy. It only copies from > > 'err.type' to 'err.mask', which is exactly required by the > > VFIO_EEH_PE_INJECT_ERR op. > > > > Signed-off-by: Wenwen Wang > > --- > > drivers/vfio/vfio_spapr_eeh.c | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/vfio/vfio_spapr_eeh.c b/drivers/vfio/vfio_spapr_eeh.c > > index 38edeb4..66634c6 100644 > > --- a/drivers/vfio/vfio_spapr_eeh.c > > +++ b/drivers/vfio/vfio_spapr_eeh.c > > @@ -37,6 +37,7 @@ long vfio_spapr_iommu_eeh_ioctl(struct iommu_group *group, > > struct eeh_pe *pe; > > struct vfio_eeh_pe_op op; > > unsigned long minsz; > > + unsigned long start, end; > > long ret = -EINVAL; > > > > switch (cmd) { > > @@ -86,10 +87,12 @@ long vfio_spapr_iommu_eeh_ioctl(struct iommu_group *group, > > ret = eeh_pe_configure(pe); > > break; > > case VFIO_EEH_PE_INJECT_ERR: > > - minsz = offsetofend(struct vfio_eeh_pe_op, err.mask); > > - if (op.argsz < minsz) > > + start = offsetof(struct vfio_eeh_pe_op, err.type); > > + end = offsetofend(struct vfio_eeh_pe_op, err.mask); > > + if (op.argsz < end) > > return -EINVAL; > > - if (copy_from_user(&op, (void __user *)arg, minsz)) > > + if (copy_from_user(&op.err, (char __user *)arg + > > + start, end - start)) > > return -EFAULT; > > > > ret = eeh_pe_inject_err(pe, op.err.type, op.err.func, > > -- > > 2.7.4 > >