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Date:   Sun, 24 Apr 2022 19:58:02 +0100
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To:     Alexandra Winter <wintera@linux.ibm.com>,
        Wenjia Zhang <wenjia@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
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Cc:     Christian Borntraeger <borntraeger@linux.ibm.com>,
        linux-s390@vger.kernel.org,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
From:   "Colin King (gmail)" <colin.i.king@gmail.com>
Subject: re: ctcm: rename READ/WRITE defines to avoid redefinitions
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Hi,

static analysis with cppcheck detected a potential null pointer 
deference with the following commit:

commit 3c09e2647b5e1f1f9fd383971468823c2505e1b0
Author: Ursula Braun <ursula.braun@de.ibm.com>
Date:   Thu Aug 12 01:58:28 2010 +0000

     ctcm: rename READ/WRITE defines to avoid redefinitions


The analysis is as follows:

drivers/s390/net/ctcm_sysfs.c:43:8: note: Assuming that condition 'priv' 
is not redundant
  if (!(priv && priv->channel[CTCM_READ] && ndev)) {
        ^
drivers/s390/net/ctcm_sysfs.c:42:9: note: Null pointer dereference
  ndev = priv->channel[CTCM_READ]->netdev;

The code in question is as follows:

         ndev = priv->channel[CTCM_READ]->netdev;

         ^^ priv may be null, as per check below but it is being 
dereferenced when assigning ndev

         if (!(priv && priv->channel[CTCM_READ] && ndev)) {
                 CTCM_DBF_TEXT(SETUP, CTC_DBF_ERROR, "bfnondev");
                 return -ENODEV;
         }

Colin