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

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Message-ID: <20220110061713.GA1951@kadam>
Date:   Mon, 10 Jan 2022 09:17:13 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] ACPI: pfr_telemetry: Fix info leak in pfrt_log_ioctl()

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.

regards,
dan carpenter