On Wed, Oct 17, 2018 at 10:45 AM Alex Williamson
<alex.williamson@xxxxxxxxxx> wrote:
>
> On Wed, 17 Oct 2018 09:32:04 -0500
> Wenwen Wang <wang6495@xxxxxxx> 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 both
> > 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.
> >
> > This patch also adds a 4-byte reserved field in the structure
> > vfio_eeh_pe_op to make sure that the u64 fields in the structure
> > vfio_eeh_pe_err are 8-byte aligned.
> >
> > Signed-off-by: Wenwen Wang <wang6495@xxxxxxx>
> > ---
> > drivers/vfio/vfio_spapr_eeh.c | 9 ++++++---
> > include/uapi/linux/vfio.h | 1 +
> > 2 files changed, 7 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);
>
> I noted in the previous version that we already have this in minsz, so
> you're fixing a redundant copy with a redundant operation.
The value in start is different from the value in minsz. So why is
this a redundant operation?
> > + 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,
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 1aa7b82..d904c42 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -729,6 +729,7 @@ struct vfio_eeh_pe_op {
> > __u32 argsz;
> > __u32 flags;
> > __u32 op;
> > + __u32 __resv;
> > union {
> > struct vfio_eeh_pe_err err;
> > };
>
> Please don't include two separate issues in the same patch. Am I also
> correct in assuming that this is untested? Thanks,
No problem. I will seperate these two patches. And yes, this is not tested.
Thanks,
Wenwen
