linux-kernel - Re: [PATCH] scsi: libfc: Fix a NULL pointer dereference in fc_lport_ptp

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Message-ID: <427c8138-b2bc-80db-2c01-24211633b0cf@suse.de>
Date:   Wed, 1 Dec 2021 07:41:19 +0100
From:   Hannes Reinecke <hare@...e.de>
To:     Zhou Qingyang <zhou1615@....edu>
Cc:     kjlu@....edu, "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Johannes Thumshirn <jth@...nel.org>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: libfc: Fix a NULL pointer dereference in
 fc_lport_ptp_setup()

On 11/30/21 6:10 PM, Zhou Qingyang wrote:
> In fc_lport_ptp_setup(), fc_rport_create() is assigned to
> lport->ptp_rdata and there is a dereference of in fc_lport_ptp_setup(),
> which could lead to a NULL pointer dereference on failure of
> fc_rport_create().
> 
> Fix this bug by adding a check of fc_rport_create().
> 
> This bug was found by a static analyzer. The analysis employs
> differential checking to identify inconsistent security operations
> (e.g., checks or kfrees) between two code paths and confirms that the
> inconsistent operations are not recovered in the current function or
> the callers, so they constitute bugs.
> 
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
> 
> Builds with CONFIG_LIBFC=m show no new warnings,
> and our static analyzer no longer warns about this code.
> 
> Fixes: 2580064b5ec6 ("scsi: libfc: Replace ->rport_create callback with function call")
> Signed-off-by: Zhou Qingyang <zhou1615@....edu>
> ---
>   drivers/scsi/libfc/fc_lport.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/scsi/libfc/fc_lport.c b/drivers/scsi/libfc/fc_lport.c
> index 19cd4a95d354..5cd716afb711 100644
> --- a/drivers/scsi/libfc/fc_lport.c
> +++ b/drivers/scsi/libfc/fc_lport.c
> @@ -241,6 +241,13 @@ static void fc_lport_ptp_setup(struct fc_lport *lport,
>   	}
>   	mutex_lock(&lport->disc.disc_mutex);
>   	lport->ptp_rdata = fc_rport_create(lport, remote_fid);
> +	if (!lport->ptp_rdata) {
> +		mutex_unlock(&lport->disc.disc_mutex);
> +		printk(KERN_WARNING "libfc: Failed to allocate for the port (%6.6x)\n",
> +				remote_fid);
> +		return;
> +	}
> +
>   	kref_get(&lport->ptp_rdata->kref);
>   	lport->ptp_rdata->ids.port_name = remote_wwpn;
>   	lport->ptp_rdata->ids.node_name = remote_wwnn;
> 
Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
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