Subject: Re: [PATCH] ieee802154: ca8210: Add missing check for kfifo_alloc() in ca8210_probe()

From: Simon Horman <[email-masked]>
Date: Fri, 8 Nov 2024 13:39:01 +0000

On Mon, Nov 04, 2024 at 11:24:42PM +0100, Keisuke Nishimura wrote:
> 
> 
> On 04/11/2024 13:12, Simon Horman wrote:
> > + Marcel
> > 
> > On Tue, Oct 29, 2024 at 07:27:12PM +0100, Keisuke Nishimura wrote:
> >> ca8210_test_interface_init() returns the result of kfifo_alloc(),
> >> which can be non-zero in case of an error. The caller, ca8210_probe(),
> >> should check the return value and do error-handling if it fails.
> >>
> >> Fixes: ded845a781a5 ("ieee802154: Add CA8210 IEEE 802.15.4 device driver")
> >> Signed-off-by: Keisuke Nishimura <[email-masked]>
> >> ---
> >>   drivers/net/ieee802154/ca8210.c | 6 +++++-
> >>   1 file changed, 5 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/net/ieee802154/ca8210.c b/drivers/net/ieee802154/ca8210.c
> >> index e685a7f946f0..753215ebc67c 100644
> >> --- a/drivers/net/ieee802154/ca8210.c
> >> +++ b/drivers/net/ieee802154/ca8210.c
> >> @@ -3072,7 +3072,11 @@ static int ca8210_probe(struct spi_device *spi_device)
> >>   	spi_set_drvdata(priv->spi, priv);
> >>   	if (IS_ENABLED(CONFIG_IEEE802154_CA8210_DEBUGFS)) {
> >>   		cascoda_api_upstream = ca8210_test_int_driver_write;
> >> -		ca8210_test_interface_init(priv);
> >> +		ret = ca8210_test_interface_init(priv);
> >> +		if (ret) {
> >> +			dev_crit(&spi_device->dev, "ca8210_test_interface_init failed\n");
> >> +			goto error;
> > 
> > Hi Nishimura-san,
> > 
> > I see that this will conditionally call kfifo_free().
> > Is that safe here? And in branches to error above this point?
> > 
> 
> Hi Horman-san,
> 
> Thank you for taking a look at this patch.
> 
> > Is that safe here?
> 
> Yes, it is safe. The failure of kfifo_alloc(&test->up_fifo,
> CA8210_TEST_INT_FIFO_SIZE, GFP_KERNEL) sets test->up_fifo.data to NULL,
> and kfifo_free() will then do kfree(test->up_fifo.data) with some minor
> clean-up.

Thanks, sounds good.

> > And in branches to error above this point?
> 
> Are you referring to the error handling for ieee802154_alloc_hw()?

Yes.

> To my
> understanding, since spi_get_drvdata() in ca8210_remove() returns NULL
> if there's an error, we shouldn’t need to call
> ca8210_test_interface_clear(). However, I’m not familiar with this code,
> so please correct me if I'm mistaken.

That makes two of us. But I don't think your patch changes this situation.
And it does improve things wrt to the problem described in your commit
message. So, while I think it would be worth looking into the error
handling for ieee802154_alloc_hw() I don't think it needs to block progress
of this patch.

Reviewed-by: Simon Horman <[email-masked]>