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Date: Wed, 31 Oct 2018 20:50:48 +0000
From: Ioannis Valasakis <code@wizofe.uk>
To: Sasha Levin <sashal@kernel.org>
Cc: outreachy-kernel@googlegroups.com, gregkh@linuxfoundation.org,
	alexander.levin@microsoft.com
Subject: Re: [Outreachy kernel] [PATCH v2] staging: gasket Create a memory
 allocation path
Message-ID: <20181031205048.GA29504@kvasir.local>
References: <20181031164753.GA14140@kvasir.local>
 <20181031165439.GU194472@sasha-vm>
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In-Reply-To: <20181031165439.GU194472@sasha-vm>
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On Wed, Oct 31, 2018 at 12:54:39PM -0400, Sasha Levin wrote:
> On Wed, Oct 31, 2018 at 04:47:54PM +0000, Ioannis Valasakis wrote:
> > Fix multiple error allocation path by using re-direction.
> > 
> > Signed-off-by: Ioannis Valasakis <code@wizofe.uk>
> > ---
> > Changes in v2:
> > 	- Specific tags for memory allocation
> > 	- Free the memory in the right way as for kfre
> > 
> > drivers/staging/gasket/gasket_interrupt.c | 14 ++++++++------
> > 1 file changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/staging/gasket/gasket_interrupt.c b/drivers/staging/gasket/gasket_interrupt.c
> > index cdfb72af1c52..23232ea8f4d9 100644
> > --- a/drivers/staging/gasket/gasket_interrupt.c
> > +++ b/drivers/staging/gasket/gasket_interrupt.c
> > @@ -348,21 +348,21 @@ int gasket_interrupt_init(struct gasket_dev *gasket_dev, const char *name,
> > 					       sizeof(struct msix_entry),
> > 					       GFP_KERNEL);
> > 	if (!interrupt_data->msix_entries) {
> > -		goto err_alloc;
> > +		goto err_free_msix;
> > 	}
> > 
> > 	interrupt_data->eventfd_ctxs = kcalloc(num_interrupts,
> > 					       sizeof(struct eventfd_ctx *),
> > 					       GFP_KERNEL);
> > 	if (!interrupt_data->eventfd_ctxs) {
> > -		goto err_alloc;
> > +		goto err_free_eventfd;
> > 	}
> > 
> > 	interrupt_data->interrupt_counts = kcalloc(num_interrupts,
> > 						   sizeof(ulong),
> > 						   GFP_KERNEL);
> > 	if (!interrupt_data->interrupt_counts) {
> > -		goto err_alloc;
> > +		goto err_free_data;
> > 	}
> > 
> > 	switch (interrupt_data->type) {
> > @@ -397,10 +397,12 @@ int gasket_interrupt_init(struct gasket_dev *gasket_dev, const char *name,
> > 
> > 	return 0;
> > 
> > -err_alloc:
> > -	kfree(interrupt_data);
> > -	kfree(interrupt_data->msix_entries);
> > +err_free_msix:
> > 	kfree(interrupt_data->eventfd_ctxs);
> > +err_free_eventfd:
> > +	kfree(interrupt_data->msix_entries);
> > +err_free_data:
> > +	kfree(interrupt_data);
> > 	return -ENOMEM;
> > }
> 
> With this code, what will happen if, for example, the last
> allocation (interrupt_data->interrupt_counts) fails?
It took my some time but I think I saw it; the mistake is that
if interrupt_data->interrupt_counts fails it should 'goto
err_free_msix'.

Same if interrupt_data->msix_entries fails it should 'goto
err_free_data'.

Is that right?

(I got very ambitious with the labels and I mixed it up ;) Any way to
make the goto labels make sense?)


> 
> --
> Thanks,
> Sasha

Best,
Ioannis