Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] iwlwifi: properly check debugfs dentry before using it
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Luca Coelho <luca@coelho.fi>
Cc:     linux-kernel@vger.kernel.org,
        Johannes Berg <johannes.berg@intel.com>,
        Emmanuel Grumbach <emmanuel.grumbach@intel.com>,
        Intel Linux Wireless <linuxwifi@intel.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        linux-wireless@vger.kernel.org,
        Luca Coelho <luciano.coelho@intel.com>,
        stable <stable@vger.kernel.org>
References: <20190122152151.16139-24-gregkh@linuxfoundation.org>
 <03bb68be-8e42-a463-2d57-3be051dc2016@redhat.com>
 <20190327012600.GA3649@kroah.com>
 <5660d50d-6cbf-3b36-6e6c-312b1617ed23@redhat.com>
 <20190327015346.GA17979@kroah.com>
 <5f9c8beda0e925b079aa9342ce1c9523659837a4.camel@coelho.fi>
 <20190330092247.GA14300@kroah.com> <20190330093152.GB14300@kroah.com>
From:   Laura Abbott <labbott@redhat.com>
Message-ID: <50bffbea-69b5-71f4-0b9c-aead1ffc54da@redhat.com>
Date:   Mon, 1 Apr 2019 08:39:26 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.6.0
MIME-Version: 1.0
In-Reply-To: <20190330093152.GB14300@kroah.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 3/30/19 2:31 AM, Greg Kroah-Hartman wrote:
> debugfs can now report an error code if something went wrong instead of
> just NULL.  So if the return value is to be used as a "real" dentry, it
> needs to be checked if it is an error before dereferencing it.
> 
> This is now happening because of ff9fb72bc077 ("debugfs: return error
> values, not NULL").  If multiple iwlwifi devices are in the system, this
> can cause problems when the driver attempts to create the main debugfs
> directory again.  Later on in the code we fail horribly by trying to
> dereference a pointer that is an error value.
> 
> Reported-by: Laura Abbott <labbott@redhat.com>

Can you add

Reported-by:  Gabriel Ramirez <gabriello.ramirez@gmail.com>

for the bugzilla reporter who took the time to do the bisect?
I'll ask for testing as well.

> Cc: Johannes Berg <johannes.berg@intel.com>
> Cc: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
> Cc: Luca Coelho <luciano.coelho@intel.com>
> Cc: Intel Linux Wireless <linuxwifi@intel.com>
> Cc: Kalle Valo <kvalo@codeaurora.org>
> Cc: stable <stable@vger.kernel.org> # 5.0
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/debugfs-vif.c b/drivers/net/wireless/intel/iwlwifi/mvm/debugfs-vif.c
> index 2453ceabf00d..6925527d8457 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mvm/debugfs-vif.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mvm/debugfs-vif.c
> @@ -774,8 +774,7 @@ void iwl_mvm_vif_dbgfs_register(struct iwl_mvm *mvm, struct ieee80211_vif *vif)
>   		return;
>   
>   	mvmvif->dbgfs_dir = debugfs_create_dir("iwlmvm", dbgfs_dir);
> -
> -	if (!mvmvif->dbgfs_dir) {
> +	if (IS_ERR_OR_NULL(mvmvif->dbgfs_dir)) {
>   		IWL_ERR(mvm, "Failed to create debugfs directory under %pd\n",
>   			dbgfs_dir);
>   		return;
>