Return-path: Received: from mail-wm0-f65.google.com ([74.125.82.65]:36685 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753120AbdDJMM5 (ORCPT ); Mon, 10 Apr 2017 08:12:57 -0400 From: Christian Lamparter To: Myungho Jung Cc: netdev@vger.kernel.org, David Miller , linux-wireless@vger.kernel.org Subject: Re: [PATCH] p54: add null pointer check before releasing socket buffer Date: Mon, 10 Apr 2017 14:12:54 +0200 Message-ID: <3716717.OUypxXNBrR@debian64> (sfid-20170410_141313_745776_53A08934) In-Reply-To: <1491801800-4371-1-git-send-email-mhjungk@gmail.com> References: <1491801800-4371-1-git-send-email-mhjungk@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: linux-wireless-owner@vger.kernel.org List-ID: (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 > --- > 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); > } > >