linux-hardening - Re: [PATCH] bus: mhi: ep: Use kcalloc() instead of kzalloc()

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Date: Fri, 2 Feb 2024 18:48:17 +0100
From: Erick Archer <erick.archer@....com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Erick Archer <erick.archer@....com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Jeffrey Hugo <quic_jhugo@...cinc.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-arm-msm@...r.kernel.org, mhi@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] bus: mhi: ep: Use kcalloc() instead of kzalloc()

Hi Dan,

On Mon, Jan 29, 2024 at 08:20:26AM +0300, Dan Carpenter wrote:
> On Sun, Jan 28, 2024 at 11:29:33AM +0100, Erick Archer wrote:
> > > It's a bit concerning that ->event_rings is set multiple times, but only
> > > allocated one time.  It's either unnecessary or there is a potential
> > > memory corruption bug.  If it's really necessary then there should be a
> > > check that the new size is <= the size of the original buffer that we
> > > allocated.
> >
> > The ->event_rings is set twice. In the mhi_ep_mmio_init function and in
> > the mhi_ep_mmio_update_ner function.
> >
>
> It's not about the type.
>
> The event_rings struct member is the number of elements in the
> mhi_cntrl->mhi_event array.  However, we ->event_rings without
> re-allocating mhi_cntrl->mhi_event so those are not in sync any more.
> So since we don't know the number of elements in the mhi_cntrl->mhi_event
> array leading to memory corruption.

Thanks for this clarification. Now I understand what you are explaining
to me.

Regards,
Erick