Re: [PATCH 5.10 540/545] tee: add overflow check in register_shm_helper()

Jens Wiklander
2022-08-22T13:08:11Z

On Mon, Aug 22, 2022 at 3:03 PM Jens Wiklander
<jens.wiklander@linaro.org> wrote:
>
> Hi,
>
> On Mon, Aug 22, 2022 at 1:15 PM Pavel Machek <pavel@denx.de> wrote:
> >
> > Hi!
> >
> > > From: Jens Wiklander <jens.wiklander@linaro.org>
> > >
> > > commit 573ae4f13f630d6660008f1974c0a8a29c30e18a upstream.
> > >
> > > With special lengths supplied by user space, register_shm_helper() has
> > > an integer overflow when calculating the number of pages covered by a
> > > supplied user space memory region.
> > >
> > > This causes internal_get_user_pages_fast() a helper function of
> > > pin_user_pages_fast() to do a NULL pointer dereference:
> >
> > Maybe this needs fixing, but this fix adds a memory leak or two. Note
> > the goto err, that needs to be done.
>
> Thanks for bringing this up. I believe the best option is to take the
> backport I just did for 5.4, it should apply cleanly on the 5.10
> stable kernel too.
>
> Greg, can you cherry-pick the 5.4 backport patch, or would you rather
> have an explicit backport for this stable kernel?

I'm sorry, I'm confused by all the backports. I haven't posted the 5.4
yet, I've only just tested it. I'll tag that backport patch for 5.10
stable too.

Thanks,
Jens

>
> Cheers,
> Jens
>
> >
> > Best regards,
> > Pavel
> >
> > Signed-off-by: Pavel Machek <pavel@denx.de>
> >
> > > +++ b/drivers/tee/tee_shm.c
> > > @@ -222,6 +222,9 @@ struct tee_shm *tee_shm_register(struct
> > > goto err;
> > > }
> > >
> > > + if (!access_ok((void __user *)addr, length))
> > > + return ERR_PTR(-EFAULT);
> > > +
> > > mutex_lock(&teedev->mutex);
> > > shm->id = idr_alloc(&teedev->idr, shm, 1, 0, GFP_KERNEL);
> > > mutex_unlock(&teedev->mutex);
> > >
> >
> >
> > diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> > index 6e662fb131d5..283fa50676a2 100644
> > --- a/drivers/tee/tee_shm.c
> > +++ b/drivers/tee/tee_shm.c
> > @@ -222,8 +222,10 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
> > goto err;
> > }
> >
> > - if (!access_ok((void __user *)addr, length))
> > - return ERR_PTR(-EFAULT);
> > + if (!access_ok((void __user *)addr, length)) {
> > + ret = ERR_PTR(-EFAULT);
> > + goto err;
> > + }
> >
> > mutex_lock(&teedev->mutex);
> > shm->id = idr_alloc(&teedev->idr, shm, 1, 0, GFP_KERNEL);
> >
> > --
> > DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
> > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany