linux-kernel - Re: [PATCH] ACPI: pfr_telemetry: Fix info leak in pfrt_log

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Date:   Mon, 10 Jan 2022 16:39:30 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Chen Yu <yu.c.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] ACPI: pfr_telemetry: Fix info leak in pfrt_log_ioctl()

On Mon, Jan 10, 2022 at 7:17 AM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> On Fri, Jan 07, 2022 at 09:46:17PM +0800, Chen Yu wrote:
> > On Fri, Jan 07, 2022 at 10:34:07AM +0300, Dan Carpenter wrote:
> > > The "data_info" struct is copied to the user.  It has a 4 byte struct
> > > hole after the last struct member so we need to memset that to avoid
> > > copying uninitialized stack data to the user.
> > >
> > > Fixes: b0013e037a8b ("ACPI: Introduce Platform Firmware Runtime Telemetry driver")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> > > ---
> > > When you're adding a new driver to the kernel then please use the new
> > > driver's prefix instead of just the subsystem prefix.
> > >
> > >  Bad: ACPI: Introduce Platform Firmware Runtime Telemetry driver
> > > Good: ACPI / pfr_telemetry: Introduce Platform Firmware Runtime Telemetry driver
> > >
> > Thanks for pointing this out.
> > > Otherwise it's just up to me to guess what prefix you wanted.
> > >
> > >  drivers/acpi/pfr_telemetry.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/acpi/pfr_telemetry.c b/drivers/acpi/pfr_telemetry.c
> > > index da50dd80192c..9abf350bd7a5 100644
> > > --- a/drivers/acpi/pfr_telemetry.c
> > > +++ b/drivers/acpi/pfr_telemetry.c
> > > @@ -83,6 +83,7 @@ static int get_pfrt_log_data_info(struct pfrt_log_data_info *data_info,
> > >     union acpi_object *out_obj, in_obj, in_buf;
> > >     int ret = -EBUSY;
> > >
> > > +   memset(data_info, 0, sizeof(*data_info));
> > Just one minor question, how about moving above before:
> > data_info->status = out_obj->package.elements[LOG_STATUS_IDX].integer.value;
> > after the sanity check of the _DSM result?
>
> I guess I wanted to keep all the memsets together.  I feel like if the
> data is invalid, then it's going to be a slow path and it's not worth
> optimizing that case.  If the data is invalid then a little slow down is
> the least of our concerns.

Patch applied, thanks!

Yu, this series needs to spend a few days more in linux-next, because
of the fixes against it sent lately.