From: imv4bel@gmail.com
To: mchehab@kernel.org
Cc: Hyunwoo Kim <imv4bel@gmail.com>,
kernel@tuxforce.de, linux-media@vger.kernel.org,
linux-usb@vger.kernel.org, cai.huoqing@linux.dev, tiwai@suse.de
Subject: [PATCH 2/4] media: dvb-core: Fix use-after-free due to race condition occurring in dvb_net
Date: Tue, 15 Nov 2022 05:18:20 -0800 [thread overview]
Message-ID: <20221115131822.6640-3-imv4bel@gmail.com> (raw)
In-Reply-To: <20221115131822.6640-1-imv4bel@gmail.com>
From: Hyunwoo Kim <imv4bel@gmail.com>
A race condition may occur between the .disconnect function, which
is called when the device is disconnected, and the dvb_device_open()
function, which is called when the device node is open()ed.
This results in several types of UAFs.
The root cause of this is that you use the dvb_device_open() function,
which does not implement a conditional statement
that checks 'dvbnet->exit'.
So, add 'remove_mutex` to protect 'dvbnet->exit' and use
locked_dvb_net_open() function to check 'dvbnet->exit'.
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
drivers/media/dvb-core/dvb_net.c | 37 +++++++++++++++++++++++++++++---
include/media/dvb_net.h | 4 ++++
2 files changed, 38 insertions(+), 3 deletions(-)
diff --git a/drivers/media/dvb-core/dvb_net.c b/drivers/media/dvb-core/dvb_net.c
index 8a2febf33ce2..bdfc6609cb93 100644
--- a/drivers/media/dvb-core/dvb_net.c
+++ b/drivers/media/dvb-core/dvb_net.c
@@ -1564,15 +1564,42 @@ static long dvb_net_ioctl(struct file *file,
return dvb_usercopy(file, cmd, arg, dvb_net_do_ioctl);
}
+static int locked_dvb_net_open(struct inode *inode, struct file *file)
+{
+ struct dvb_device *dvbdev = file->private_data;
+ struct dvb_net *dvbnet = dvbdev->priv;
+ int ret;
+
+ if (mutex_lock_interruptible(&dvbnet->remove_mutex))
+ return -ERESTARTSYS;
+
+ if (dvbnet->exit) {
+ mutex_unlock(&dvbnet->remove_mutex);
+ return -ENODEV;
+ }
+
+ ret = dvb_generic_open(inode, file);
+
+ mutex_unlock(&dvbnet->remove_mutex);
+
+ return ret;
+}
+
static int dvb_net_close(struct inode *inode, struct file *file)
{
struct dvb_device *dvbdev = file->private_data;
struct dvb_net *dvbnet = dvbdev->priv;
+ mutex_lock(&dvbnet->remove_mutex);
+
dvb_generic_release(inode, file);
- if(dvbdev->users == 1 && dvbnet->exit == 1)
+ if (dvbdev->users == 1 && dvbnet->exit == 1) {
+ mutex_unlock(&dvbnet->remove_mutex);
wake_up(&dvbdev->wait_queue);
+ } else
+ mutex_unlock(&dvbnet->remove_mutex);
+
return 0;
}
@@ -1580,7 +1607,7 @@ static int dvb_net_close(struct inode *inode, struct file *file)
static const struct file_operations dvb_net_fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = dvb_net_ioctl,
- .open = dvb_generic_open,
+ .open = locked_dvb_net_open,
.release = dvb_net_close,
.llseek = noop_llseek,
};
@@ -1599,10 +1626,13 @@ void dvb_net_release (struct dvb_net *dvbnet)
{
int i;
+ mutex_lock(&dvbnet->remove_mutex);
dvbnet->exit = 1;
+ mutex_unlock(&dvbnet->remove_mutex);
+
if (dvbnet->dvbdev->users < 1)
wait_event(dvbnet->dvbdev->wait_queue,
- dvbnet->dvbdev->users==1);
+ dvbnet->dvbdev->users == 1);
dvb_unregister_device(dvbnet->dvbdev);
@@ -1621,6 +1651,7 @@ int dvb_net_init (struct dvb_adapter *adap, struct dvb_net *dvbnet,
int i;
mutex_init(&dvbnet->ioctl_mutex);
+ mutex_init(&dvbnet->remove_mutex);
dvbnet->demux = dmx;
for (i=0; i<DVB_NET_DEVICES_MAX; i++)
diff --git a/include/media/dvb_net.h b/include/media/dvb_net.h
index 5e31d37f25fa..3e2eee5a05e5 100644
--- a/include/media/dvb_net.h
+++ b/include/media/dvb_net.h
@@ -41,6 +41,9 @@
* @exit: flag to indicate when the device is being removed.
* @demux: pointer to &struct dmx_demux.
* @ioctl_mutex: protect access to this struct.
+ * @remove_mutex: mutex that avoids a race condition between a callback
+ * called when the hardware is disconnected and the
+ * file_operations of dvb_net
*
* Currently, the core supports up to %DVB_NET_DEVICES_MAX (10) network
* devices.
@@ -53,6 +56,7 @@ struct dvb_net {
unsigned int exit:1;
struct dmx_demux *demux;
struct mutex ioctl_mutex;
+ struct mutex remove_mutex;
};
/**
--
2.25.1
next prev parent reply other threads:[~2022-11-15 13:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-15 13:18 [PATCH 0/4] Fix multiple race condition vulnerabilities in dvb-core and device driver imv4bel
2022-11-15 13:18 ` [PATCH 1/4] media: dvb-core: Fix use-after-free due to race condition occurring in dvb_frontend imv4bel
2022-11-15 13:18 ` imv4bel [this message]
2022-11-15 13:18 ` [PATCH 3/4] media: dvb-core: Fix use-after-free due to race condition occurring in dvb_register_device() imv4bel
2022-11-17 4:16 ` Dan Carpenter
2022-11-15 13:18 ` [PATCH 4/4] media: ttusb-dec: Fix memory leak in ttusb_dec_exit_dvb() imv4bel
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