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

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Message-ID: <20140220090339.GW26722@mwanda>
Date:	Thu, 20 Feb 2014 12:03:39 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	"Zhao, Gang" <gamerh2o@...il.com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	devel@...verdev.osuosl.org, mark.einon@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] et131x: fix allocation failures

On Thu, Feb 20, 2014 at 11:03:45AM +0800, Zhao, Gang wrote:
> On Wed, 2014-02-19 at 19:43:15 +0800, One Thousand Gnomes wrote:
> > 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.
> >
> 
> Yes, you are right. By calling {tx, rx}_dma_memory_free the memory will
> be freed.
> 
> But I think a comment is needed here, to make this more clear ? Without
> proper comment the above code looks a little strange to let one think
> it's right. :)

No.  We don't need a comment.  If people start adding kfree() calls
all over the place without thinking then we are already screwed and no
comment is going to help us.

regards,
dan carpenter

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