linux-kernel - Re: [PATCH] et131x: fix allocation failures

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Message-ID: <20140219114315.5af78dfe@alan.etchedpixels.co.uk>
Date:	Wed, 19 Feb 2014 11:43:15 +0000
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	"Zhao\, Gang" <gamerh2o@...il.com>
Cc:	devel@...verdev.osuosl.org, mark.einon@...il.com,
	linux-kernel@...r.kernel.org, greg@...ah.com
Subject: Re: [PATCH] et131x: fix allocation failures

On Wed, 19 Feb 2014 09:14:19 +0800
"Zhao\, Gang" <gamerh2o@...il.com> wrote:

> Alan, thanks for resending this patch. But it seems you overlooked
> something we discussed earlier.
> 
> On Mon, 2014-02-17 at 22:13:08 +0800, Alan wrote:
> > We should check the ring allocations don't fail.
> > If we get a fail we need to clean up properly. The allocator assumes the
> > deallocator will be used on failure, but it isn't. Make sure the
> > right deallocator is always called and add a missing check against
> > fbr allocation failure.
> >
> > [v2]: Correct check logic
> >
> > Signed-off-by: Alan Cox <alan@...ux.intel.com>
> > ---
> >  drivers/staging/et131x/et131x.c |    9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/et131x/et131x.c b/drivers/staging/et131x/et131x.c
> > index 6413500..cc600df 100644
> > --- a/drivers/staging/et131x/et131x.c
> > +++ b/drivers/staging/et131x/et131x.c
> > @@ -2124,7 +2124,11 @@ static int et131x_rx_dma_memory_alloc(struct et131x_adapter *adapter)
> >  
> >  	/* Alloc memory for the lookup table */
> >  	rx_ring->fbr[0] = kmalloc(sizeof(struct fbr_lookup), GFP_KERNEL);
> > +	if (rx_ring->fbr[0] == NULL)
> > +		return -ENOMEM;
> >  	rx_ring->fbr[1] = kmalloc(sizeof(struct fbr_lookup), GFP_KERNEL);
> > +	if (rx_ring->fbr[1] == NULL)
> > +		return -ENOMEM;
> 
> Shouldn't rx_ring->fbr[0] be freed when allocation of rx_ring->fbr[1]
> fails ? Or we will leak memory here.

No.. the tx_dma_memory_free and rx_dma_memory_free functions are
designed to handle incomplete set up. They are now called on incomplete
setup and will clean up all the resources.

> > @@ -3591,6 +3595,7 @@ static int et131x_adapter_memory_alloc(struct et131x_adapter *adapter)
> >  	if (status) {
> >  		dev_err(&adapter->pdev->dev,
> >  			  "et131x_tx_dma_memory_alloc FAILED\n");
> > +		et131x_tx_dma_memory_free(adapter);
> >  		return status;
> >  	}
> >  	/* Receive buffer memory allocation */
> > @@ -3598,7 +3603,7 @@ static int et131x_adapter_memory_alloc(struct et131x_adapter *adapter)
> >  	if (status) {
> >  		dev_err(&adapter->pdev->dev,
> >  			  "et131x_rx_dma_memory_alloc FAILED\n");
> > -		et131x_tx_dma_memory_free(adapter);
> > +		et131x_adapter_memory_free(adapter);
> >  		return status;
> >  	}
> >  

Which is what these changes are about.

Whoever wrote the allocator and cleanup methods arranged (except for the
rx_ring->fbr cases) that the free method should be called on a failure.
It looks as if somewhere along the line of the driver development whoever
wrote the higher level bits didn't understand that.

Alan
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