On Mon, Apr 10, 2017 at 02:12:54PM +0200, Christian Lamparter wrote: > (Added linux-wireless, since this is a wireless driver) > > On Sunday, April 9, 2017 10:23:20 PM CEST Myungho Jung wrote: > > Kernel panic is caused by trying to dereference null pointer. Check if > > the pointer is null before freeing space. > Do you have the kernel panic somewhere? > I think you have an even bigger problem: You see, in order to get EEPROM > readback and rx_stats feedback you need to sent a request to the firmware > and if the response's req_id cookies don't match, you end up filling up > the very limited device address space. > > As for adding if (!skb) checks. I think kfree, kfree_skb, dev_kfree_skb > (aka consume_skb) all check for null pointers already. So the logical > thing to do would be to make dev_kfree_skb_irq (which would also fix > dev_kfree_skb_any) consistent with kfree, kfree_skb, dev_kfree_skb and > add the check there. > > > Signed-off-by: Myungho Jung <mhjungk@xxxxxxxxx> > > --- > > drivers/net/wireless/intersil/p54/txrx.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/net/wireless/intersil/p54/txrx.c b/drivers/net/wireless/intersil/p54/txrx.c > > index 1af7da0..8956061 100644 > > --- a/drivers/net/wireless/intersil/p54/txrx.c > > +++ b/drivers/net/wireless/intersil/p54/txrx.c > > @@ -503,7 +503,9 @@ static void p54_rx_eeprom_readback(struct p54_common *priv, > > > > priv->eeprom = NULL; > > tmp = p54_find_and_unlink_skb(priv, hdr->req_id); > > - dev_kfree_skb_any(tmp); > > + if (unlikely(!tmp)) > > + dev_kfree_skb_any(tmp); > > + > > complete(&priv->eeprom_comp); > > } > > > > @@ -597,7 +599,9 @@ static void p54_rx_stats(struct p54_common *priv, struct sk_buff *skb) > > } > > > > tmp = p54_find_and_unlink_skb(priv, hdr->req_id); > > - dev_kfree_skb_any(tmp); > > + if (unlikely(!tmp)) > > + dev_kfree_skb_any(tmp); > > + > > complete(&priv->stat_comp); > > } > > > > > > I found that the fix was totally opposite to my thought. Sorry about confusion. I'm not sure it actually caused kernel panic but guessed from a bug report [https://bugzilla.kernel.org/show_bug.cgi?id=195289]. And correct fix will be like this: if (likely(tmp)) dev_kfree_skb_any(tmp); But, like you said, I think null pointer should be checked in dev_kfree_skb_irq although already checking before calling it in many other places. I'll try another patch. Thank you for your advice. Thanks, Myungho
