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Message-ID: <YyQxuHi2iQIvj0Lj@kadam>
Date: Fri, 16 Sep 2022 11:20:08 +0300
From: Dan Carpenter <dan.carpenter@...cle.com>
To: Kees Cook <keescook@...omium.org>
Cc: Peter Rosin <peda@...ntia.se>, Wolfram Sang <wsa@...nel.org>,
"Gustavo A. R. Silva" <gustavo@...eddedor.com>,
linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] i2c: mux: harden i2c_mux_alloc() against integer
overflows
On Fri, Sep 16, 2022 at 01:01:42AM -0700, Kees Cook wrote:
> > diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
> > index 774507b54b57..313904be5f3b 100644
> > --- a/drivers/i2c/i2c-mux.c
> > +++ b/drivers/i2c/i2c-mux.c
> > @@ -243,9 +243,10 @@ struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
> > int (*deselect)(struct i2c_mux_core *, u32))
> > {
> > struct i2c_mux_core *muxc;
> > + size_t mux_size;
> >
> > - muxc = devm_kzalloc(dev, struct_size(muxc, adapter, max_adapters)
> > - + sizeof_priv, GFP_KERNEL);
> > + mux_size = struct_size(muxc, adapter, max_adapters);
> > + muxc = devm_kzalloc(dev, size_add(mux_size, sizeof_priv), GFP_KERNEL);
> > if (!muxc)
> > return NULL;
> > if (sizeof_priv)
>
> The new variable makes it more readable, but beyond that, do you see any
> reason not to just directly compose the calls?
>
You could do that too.
You pointed this out in your other email but the one thing that people
have to be careful of when assigning struct_size() is that the
"mux_size" variable has to be size_t.
The math in submit_create() from drivers/gpu/drm/msm/msm_gem_submit.c
is so terribly unreadable. It works but it's so ugly. Unfortunately,
I'm the person who wrote it.
regards,
dan carpenter
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