[openib-general] Data structure size mismatch

[Pradeep Satyanarayana]

Hal Rosenstock <halr at voltaire.com> wrote on 11/04/2005 02:30:49 PM:

> On Fri, 2005-11-04 at 17:06, Pradeep Satyanarayana wrote:
> > I realize that address translation will be replaced shortly. However,
> > here are a few things that
> > I observed which I believe are important.
>
> Important to fix in what time frame ?
>
> > I recently saw an e-mail thread about compilation problems and
> > data structure padding; this is in line with that.
> >
> > So that new incarnation does not face the same pitfalls of address
> > translation, I will describe them here.
> >
> > When I tried running uatt it fails with -EFAULT. Debug revealed that
> > it fails. The following
> > copy_from_user() fails.
> >
> > ib_route = kmalloc(sizeof *ib_route, GFP_KERNEL);
> > if (!ib_route) {
> > result = -ENOMEM;
> > goto err1;
> > }
> >
> > if (copy_from_user(ib_route, cmd.ib_route, sizeof(ib_route))) {
> > result = -EFAULT;
> > goto err2;
> > }
> >
> > In fact I believe this copy_from_user() is unnecessary since this will
> > be actually filled in by "address translation" and
> > passed back to user space later on.
>
> Not always. If I recall correctly, there is a case where this copy is
> needed. It is not in the mode that uatt uses AT right now though.

Maybe true, but there is still a 32-bit app 64-bit kernel issue that needs
to be
fixed, unless we agree to change the data structure to say incorporate a
device_name
as you suggest below.


>
> >  So, if I eliminate this copy_from_user(), uatt again fails with
> > EFAULT in:
> >
> > if (copy_to_user((void __user *)(unsigned long)cmd.response,
> > &resp, sizeof(resp))) {
> > result = -EFAULT;
> > goto err4;
> > }
> >
> > The environment I was using a 32-bit app and 64-bit kernel on Power.
> > The reason is
> > struct ib_uat_route_by_ip_req has pointers in them (LP64 vs ILP32).
>
> This needs to be replaced by the port GID. Another alternative is the
> name. This has been discussed before on the list.
>
> -- Hal
>
> > I am told a 64-bit app succeeded on a 64-bit kernel which confirmed my
> > suspicions.
> >
> > Given that I took a quick look at all the places that copy_from_user()
> > is used (I did not
> > do this exercise for copy_to_user(), which would be the complete thing
> > to do) and found
> > that this (data structure size mismatch) potentially also occurs in
> > user_mad,c. I did not see any anomalies

Even if we change struct ib_uat_route_by_ip_req, there still is user_mad.c
that
needs to be looked into.


Pradeep
pradeep at us.ibm.com

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