linux-kernel - [PATCH v2 3/9] pps: Fix a use-after free bug when unregistering a source.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <9a0942515d100e71c19c3471d50bead14e722421.1360677367.git.linux@horizon.com>
Date:	Tue, 12 Feb 2013 02:27:20 -0500
From:	George Spelvin <linux@...izon.com>
To:	linux-serial@...r.kernel.org, peter@...leysoftware.com,
	gregkh@...uxfoundation.org
Cc:	linux-kernel@...r.kernel.org, giometti@...ux.it, linux@...izon.com
Subject: [PATCH v2 3/9] pps: Fix a use-after free bug when unregistering a
 source.

Remove the cdev from the system (with cdev_del) *before* deallocating it
(in pps_device_destruct, called via kobject_put from device_destroy).

Also prevent deallocating a device with open file handles.

A better long-term fix is probably to remove the cdev from the pps_device
entirely, and instead have all devices reference one global cdev.  Then
the deallocation ordering becomes simpler.

But that's more complex and invasive change, so we leave that
for later.

Signed-off-by: George Spelvin <linux@...izon.com>
Cc: stable@...nel.org
---
 drivers/pps/pps.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index a70e384..6437703 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -247,12 +247,15 @@ static int pps_cdev_open(struct inode *inode, struct file *file)
 	struct pps_device *pps = container_of(inode->i_cdev,
 						struct pps_device, cdev);
 	file->private_data = pps;
-
+	kobject_get(&pps->dev->kobj);
 	return 0;
 }
 
 static int pps_cdev_release(struct inode *inode, struct file *file)
 {
+	struct pps_device *pps = container_of(inode->i_cdev,
+						struct pps_device, cdev);
+	kobject_put(&pps->dev->kobj);
 	return 0;
 }
 
@@ -274,8 +277,10 @@ static void pps_device_destruct(struct device *dev)
 {
 	struct pps_device *pps = dev_get_drvdata(dev);
 
-	/* release id here to protect others from using it while it's
-	 * still in use */
+	cdev_del(&pps->cdev);
+
+	/* Now we can release the ID for re-use */
+	pr_debug("deallocating pps%d\n", pps->id);
 	mutex_lock(&pps_idr_lock);
 	idr_remove(&pps_idr, pps->id);
 	mutex_unlock(&pps_idr_lock);
@@ -332,6 +337,7 @@ int pps_register_cdev(struct pps_device *pps)
 		goto del_cdev;
 	}
 
+	/* Override the release function with our own */
 	pps->dev->release = pps_device_destruct;
 
 	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
@@ -352,9 +358,9 @@ free_idr:
 
 void pps_unregister_cdev(struct pps_device *pps)
 {
+	pr_debug("unregistering pps%d\n", pps->id);
 	pps->lookup_cookie = NULL;
 	device_destroy(pps_class, pps->dev->devt);
-	cdev_del(&pps->cdev);
 }
 
 /*
-- 
1.8.1.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/