linux-kernel - Re: [PATCH] Input: cyttsp4 - Fix error on calculating memory size passed to krealloc.

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Date:   Thu, 2 Nov 2017 16:54:51 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Vince Kim <vince.k.kim@...il.com>
Cc:     Ferruh Yigit <fery@...ress.com>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: cyttsp4 - Fix error on calculating memory size
 passed to krealloc.

Hi Vince,

On Wed, Nov 01, 2017 at 09:13:58PM -0700, Vince Kim wrote:
> It looks patch send to the maintainer rejected.
> 

I can take the patch, but I need your signed-off-by please.

> Can anyone take a look?
> 
> 
> 
> *==============================*
> 
> *Delivery has failed to these recipients or groups:*
> 
> Ferruh Yigit (fery@...ress.com) <fery@...ress.com>
> Your message wasn't delivered due to a permission or security issue. It may
> have been rejected by a moderator, the address may only accept e-mail from
> certain senders, or another restriction may be preventing delivery.
> *==============================*
> 
> On Tue, Oct 31, 2017 at 12:19 PM, Vince Kim <vince.k.kim@...il.com> wrote:
> 
> > There are several places to perform subtraction to calculate buffer
> > size such as:
> >
> > si->si_ofs.cydata_size = si->si_ofs.test_ofs - si->si_ofs.cydata_ofs;
> > ...
> > p = krealloc(si->si_ptrs.cydata, si->si_ofs.cydata_size, GFP_KERNEL);
> >
> > Actually, data types of above variables during subtraction are size_t, so
> > it is
> > unsigned. That means if second operand(si->si_ofs.cydata_ofs) is
> > greater than the first operand(si->si_ofs.test_ofs), then resulting
> > si->si_ofs.cydata_size could result in an unsigned integer wrap which is
> > not desiarable.
> >
> > The properway to correct this problem is to perform a test of both
> > operands to avoid having unsigned wrap.
> > ---
> >  drivers/input/touchscreen/cyttsp4_core.c | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> >
> > diff --git a/drivers/input/touchscreen/cyttsp4_core.c
> > b/drivers/input/touchscreen/cyttsp4_core.c
> > index beaf61c..eecc7f1 100644
> > --- a/drivers/input/touchscreen/cyttsp4_core.c
> > +++ b/drivers/input/touchscreen/cyttsp4_core.c
> > @@ -201,6 +201,11 @@ static int cyttsp4_si_get_cydata(struct cyttsp4 *cd)
> >         void *p;
> >         int rc;
> >
> > +       if (si->si_ofs.test_ofs <= si->si_ofs.cydata_ofs)
> > +               dev_err(cd->dev, "%s: invalid offset  test_ofs:%zd,
> > cydata_ofs:%zd \n", __func__, si->si_ofs.test_ofs, si->si_ofs.cydata_ofs);
> > +               return -EINVAL;
> > +       }
> > +
> >         si->si_ofs.cydata_size = si->si_ofs.test_ofs -
> > si->si_ofs.cydata_ofs;
> >         dev_dbg(cd->dev, "%s: cydata size: %zd\n", __func__,
> >                         si->si_ofs.cydata_size);
> > @@ -270,6 +275,11 @@ static int cyttsp4_si_get_test_data(struct cyttsp4
> > *cd)
> >         void *p;
> >         int rc;
> >
> > +       if (si->si_ofs.pcfg_ofs <= si->si_ofs.test_ofs)
> > +               dev_err(cd->dev, "%s: invalid offset  pcfg_ofs:%zd,
> > test_ofs:%zd \n", __func__, si->si_ofs.pcfg_ofs, si->si_ofs.test_ofs);
> > +               return -EINVAL;
> > +       }
> > +
> >         si->si_ofs.test_size = si->si_ofs.pcfg_ofs - si->si_ofs.test_ofs;
> >
> >         p = krealloc(si->si_ptrs.test, si->si_ofs.test_size, GFP_KERNEL);
> > @@ -321,6 +331,11 @@ static int cyttsp4_si_get_pcfg_data(struct cyttsp4
> > *cd)
> >         void *p;
> >         int rc;
> >
> > +       if (si->si_ofs.opcfg_ofs <= si->si_ofs.pcfg_ofs)
> > +               dev_err(cd->dev, "%s: invalid offset  opcfg_ofs:%zd,
> > pcfg_ofs:%zd \n", __func__, si->si_ofs.opcfg_ofs, si->si_ofs.pcfg_ofs);
> > +               return -EINVAL;
> > +       }
> > +
> >         si->si_ofs.pcfg_size = si->si_ofs.opcfg_ofs - si->si_ofs.pcfg_ofs;
> >
> >         p = krealloc(si->si_ptrs.pcfg, si->si_ofs.pcfg_size, GFP_KERNEL);
> > @@ -367,6 +382,11 @@ static int cyttsp4_si_get_opcfg_data(struct cyttsp4
> > *cd)
> >         void *p;
> >         int rc;
> >
> > +       if (si->si_ofs.ddata_ofs <= si->si_ofs.opcfg_ofs)
> > +               dev_err(cd->dev, "%s: invalid offset  ddata_ofs:%zd,
> > opcfg_ofs:%zd \n", __func__, si->si_ofs.ddata_ofs, si->si_ofs.opcfg_ofs);
> > +               return -EINVAL;
> > +       }
> > +
> >         si->si_ofs.opcfg_size = si->si_ofs.ddata_ofs -
> > si->si_ofs.opcfg_ofs;
> >
> >         p = krealloc(si->si_ptrs.opcfg, si->si_ofs.opcfg_size, GFP_KERNEL);
> > --
> > 2.7.4
> >
> >

-- 
Dmitry