linux-kernel - Re: [PATCH] staging: media: atomisp: Fix premature setting of HMM_BO_DEVICE

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Message-ID: <aGPYZhK65LaD0wVO@smile.fi.intel.com>
Date: Tue, 1 Jul 2025 15:45:26 +0300
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Abdelrahman Fekry <abdelrahmanfekry375@...il.com>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>, andy@...nel.org,
	hdegoede@...hat.com, mchehab@...nel.org,
	sakari.ailus@...ux.intel.com, gregkh@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
	skhan@...uxfoundation.com, dan.carpenter@...aro.org
Subject: Re: [PATCH] staging: media: atomisp: Fix premature setting of
 HMM_BO_DEVICE_INITED flag

On Tue, Jul 01, 2025 at 02:58:43PM +0300, Abdelrahman Fekry wrote:
> Hello Andy,
> On Sat, Jun 28, 2025 at 10:52 PM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
> > On Sat, Jun 28, 2025 at 8:26 AM Abdelrahman Fekry
> > <abdelrahmanfekry375@...il.com> wrote:

> > > The HMM_BO_DEVICE_INITED flag was being set in hmm_bo_device_init()
> > > before key initialization steps like kmem_cache_create(),
> > > kmem_cache_alloc(), and __bo_init().
> > >
> > > This means that if any of these steps fail, the flag remains set,
> > > misleading other parts of the driver (e.g. hmm_bo_alloc())
> > > into thinking the device is initialized. This could lead
> > > to undefined behavior or invalid memory use.
> >
> > Nice. Can you make some fault injection (temporary by modifying the
> > code to always fail, for example) and actually prove this in practice?
> > If so, the few (important) lines from the given Oops would be nice to
> > have here.

> I have been trying to test it without having any intel atomisp
> hardware and failed continuously, do you have any tips or maybe some
> resources on how i can test this driver.

So, the easiest way as I can see it is to ask people who possess the HW to
test, but you need to provide a testing patch (which can be applied on top
of this one, for example).

> > > Additionally, since __bo_init() is called from inside
> > > hmm_bo_device_init() after the flag was already set, its internal
> > > check for HMM_BO_DEVICE_INITED is redundant.
> > >
> > > - Move the flag assignment to the end after all allocations succeed.
> > > - Remove redundant check of the flag inside __bo_init()

-- 
With Best Regards,
Andy Shevchenko