On Wed, 11 Apr 2018 02:37:44 +0200,
Ram Pai wrote:
>
> On Tue, Apr 10, 2018 at 01:42:39PM -0700, Andrew Morton wrote:
> > On Tue, 10 Apr 2018 06:54:11 +0200 Takashi Iwai <ti...@suse.de> wrote:
> >
> > > On Tue, 10 Apr 2018 02:23:26 +0200,
> > > Andrew Morton wrote:
> > > >
> > > > On Sun, 8 Apr 2018 09:20:26 +0200 Takashi Iwai <ti...@suse.de> wrote:
> > > >
> > > > > We've got a bug report indicating a kernel panic at booting on an
> > > > > x86-32 system, and it turned out to be the invalid resource assigned
> > > > > after PCI resource reallocation. __find_resource() first aligns the
> > > > > resource start address and resets the end address with start+size-1
> > > > > accordingly, then checks whether it's contained. Here the end address
> > > > > may overflow the integer, although resource_contains() still returns
> > > > > true because the function validates only start and end address. So
> > > > > this ends up with returning an invalid resource (start > end).
> > > > >
> > > > > There was already an attempt to cover such a problem in the commit
> > > > > 47ea91b4052d ("Resource: fix wrong resource window calculation"), but
> > > > > this case is an overseen one.
> > > > >
> > > > > This patch adds the validity check in resource_contains() to see
> > > > > whether the given resource has a valid range for avoiding the integer
> > > > > overflow problem.
> > > > >
> > > > > ...
> > > > >
> > > > > --- a/include/linux/ioport.h
> > > > > +++ b/include/linux/ioport.h
> > > > > @@ -212,6 +212,9 @@ static inline bool resource_contains(struct
> > > > > resource *r1, struct resource *r2)
> > > > > return false;
> > > > > if (r1->flags & IORESOURCE_UNSET || r2->flags &
> > > > > IORESOURCE_UNSET)
> > > > > return false;
> > > > > + /* sanity check whether it's a valid resource range */
> > > > > + if (r2->end < r2->start)
> > > > > + return false;
> > > > > return r1->start <= r2->start && r1->end >= r2->end;
> > > > > }
> > > >
> > > > This doesn't look like the correct place to handle this? Clearly .end
> > > > < .start is an invalid state for a resource and we should never have
> > > > constructed such a thing in the first place? So adding a check at the
> > > > place where this resource was initially created seems to be the correct
> > > > fix?
> > >
> > > Yes, that was also my first thought and actually the v1 patch was like
> > > that.
> >
> > Yes, I do prefer.
> >
> > > The v2 one was by Ram's suggestion so that we can cover
> > > potential bugs by all other callers as well.
> >
> > That could be done as a separate thing?
>
> the first approach will fix overflows in just that particular case. The
> second approach will catch and error-out overflows anywhere. There is a
> short-term down side to the second approach; it might cause a slew of
> error reports but will eventually help clean up all bad behavior.
For that purpose, maybe we should do in two folds: at first fix this
specific issue in __find_resource(), then put the sanity check in
resource_contains() in addition but with WARN_ON() so that we can
catch more obviously.
thanks,
Takashi
