Re: [PATCH] mpt3sas_ctl: fix double-fetch bug in _ctl_ioctl_main()

[Gen Zhang]

On Tue, May 28, 2019 at 11:44:35AM +0530, Suganath Prabu Subramani wrote:
> Please consider this patch as Ack-by: Suganath Prabu S
> <suganath-prabu.subramani@xxxxxxxxxxxx>
> 
> Thanks,
> Suganath.
> 
> 
> On Mon, May 27, 2019 at 6:27 AM Gen Zhang <blackgod016574@xxxxxxxxx> wrote:
> >
> > In _ctl_ioctl_main(), 'ioctl_header' is fetched the first time from
> > userspace. 'ioctl_header.ioc_number' is then checked. The legal result
> > is saved to 'ioc'. Then, in condition MPT3COMMAND, the whole struct is
> > fetched again from the userspace. Then _ctl_do_mpt_command() is called,
> > 'ioc' and 'karg' as inputs.
> >
> > However, a malicious user can change the 'ioc_number' between the two
> > fetches, which will cause a potential security issues.  Moreover, a
> > malicious user can provide a valid 'ioc_number' to pass the check in
> > first fetch, and then modify it in the second fetch.
> >
> > To fix this, we need to recheck the 'ioc_number' in the second fetch.
> >
> > Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx>
> > ---
> > diff --git a/drivers/scsi/mpt3sas/mpt3sas_ctl.c b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> > index b2bb47c..5181c03 100644
> > --- a/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> > +++ b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> > @@ -2319,6 +2319,10 @@ _ctl_ioctl_main(struct file *file, unsigned int cmd, void __user *arg,
> >                         break;
> >                 }
> >
> > +               if (karg.hdr.ioc_number != ioctl_header.ioc_number) {
> > +                       ret = -EINVAL;
> > +                       break;
> > +               }
> >                 if (_IOC_SIZE(cmd) == sizeof(struct mpt3_ioctl_command)) {
> >                         uarg = arg;
> >                         ret = _ctl_do_mpt_command(ioc, karg, &uarg->mf);
Thanks for your reply, Suganath.

Thanks
Gen