linux-kernel - [PATCH] ppdev: don't print a free'd string

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Message-Id: <20161202162355.25470-1-colin.king@canonical.com>
Date:   Fri,  2 Dec 2016 16:23:55 +0000
From:   Colin King <colin.king@...onical.com>
To:     Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] ppdev: don't print a free'd string

From: Colin Ian King <colin.king@...onical.com>

A previous fix of a memory leak now prints the string 'name'
that was previously free'd.  Fix this by free'ing the string
at the end of the function and adding an error exit path for
the error conditions.

CoverityScan CID#1384523 ("Use after free")

Fixes: 2bd362d5f45c1 ("ppdev: fix memory leak")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/char/ppdev.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
index 02819e0..4cf6d68 100644
--- a/drivers/char/ppdev.c
+++ b/drivers/char/ppdev.c
@@ -290,6 +290,7 @@ static int register_device(int minor, struct pp_struct *pp)
 	struct pardevice *pdev = NULL;
 	char *name;
 	struct pardev_cb ppdev_cb;
+	int rc = 0;
 
 	name = kasprintf(GFP_KERNEL, CHRDEV "%x", minor);
 	if (name == NULL)
@@ -298,8 +299,8 @@ static int register_device(int minor, struct pp_struct *pp)
 	port = parport_find_number(minor);
 	if (!port) {
 		pr_warn("%s: no associated port!\n", name);
-		kfree(name);
-		return -ENXIO;
+		rc = -ENXIO;
+		goto err;
 	}
 
 	memset(&ppdev_cb, 0, sizeof(ppdev_cb));
@@ -308,16 +309,18 @@ static int register_device(int minor, struct pp_struct *pp)
 	ppdev_cb.private = pp;
 	pdev = parport_register_dev_model(port, name, &ppdev_cb, minor);
 	parport_put_port(port);
-	kfree(name);
 
 	if (!pdev) {
 		pr_warn("%s: failed to register device!\n", name);
-		return -ENXIO;
+		rc = -ENXIO;
+		goto err;
 	}
 
 	pp->pdev = pdev;
 	dev_dbg(&pdev->dev, "registered pardevice\n");
-	return 0;
+err:
+	kfree(name);
+	return rc;
 }
 
 static enum ieee1284_phase init_phase(int mode)
-- 
2.10.2