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

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Message-Id: <20211130171049.199111-1-zhou1615@umn.edu>
Date:   Wed,  1 Dec 2021 01:10:49 +0800
From:   Zhou Qingyang <zhou1615@....edu>
To:     zhou1615@....edu
Cc:     kjlu@....edu, Hannes Reinecke <hare@...e.de>,
        "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: [PATCH] scsi: libfc: Fix a NULL pointer dereference in fc_lport_ptp_setup()

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;
-- 
2.25.1