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media: dvb-core: Fix use-after-free due to race condition at dvb_ca_en50221 

If the device node of dvb_ca_en50221 is open() and the
device is disconnected, a UAF may occur when calling
close() on the device node.

The root cause is that wake_up() and wait_event() for
dvbdev->wait_queue are not implemented.

So implement wait_event() function in dvb_ca_en50221_release()
and add 'remove_mutex' which prevents race condition
for 'ca->exit'.

[mchehab: fix a checkpatch warning]

Link: https://lore.kernel.org/linux-media/20221121063308.GA33821@ubuntu
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
This commit is contained in:
Hyunwoo Kim 2022-11-21 06:33:08 +00:00 committed by Mauro Carvalho Chehab
parent b8c75e4a1b
commit 280a8ab817
1 changed files with 36 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
drivers/media/dvb-core/dvb_ca_en50221.c
View File

@ -151,6 +151,12 @@ struct dvb_ca_private {
/* mutex serializing ioctls */
struct mutex ioctl_mutex;
/* A mutex used when a device is disconnected */
struct mutex remove_mutex;
/* Whether the device is disconnected */
int exit;
};
static void dvb_ca_private_free(struct dvb_ca_private *ca)
@ -1711,12 +1717,22 @@ static int dvb_ca_en50221_io_open(struct inode *inode, struct file *file)
dprintk("%s\n", __func__);
if (!try_module_get(ca->pub->owner))
mutex_lock(&ca->remove_mutex);
if (ca->exit) {
mutex_unlock(&ca->remove_mutex);
return -ENODEV;
}
if (!try_module_get(ca->pub->owner)) {
mutex_unlock(&ca->remove_mutex);
return -EIO;
}
err = dvb_generic_open(inode, file);
if (err < 0) {
module_put(ca->pub->owner);
mutex_unlock(&ca->remove_mutex);
return err;
}
@ -1741,6 +1757,7 @@ static int dvb_ca_en50221_io_open(struct inode *inode, struct file *file)
dvb_ca_private_get(ca);
mutex_unlock(&ca->remove_mutex);
return 0;
}
@ -1760,6 +1777,8 @@ static int dvb_ca_en50221_io_release(struct inode *inode, struct file *file)
dprintk("%s\n", __func__);
mutex_lock(&ca->remove_mutex);
/* mark the CA device as closed */
ca->open = 0;
dvb_ca_en50221_thread_update_delay(ca);
@ -1770,6 +1789,13 @@ static int dvb_ca_en50221_io_release(struct inode *inode, struct file *file)
dvb_ca_private_put(ca);
if (dvbdev->users == 1 && ca->exit == 1) {
mutex_unlock(&ca->remove_mutex);
wake_up(&dvbdev->wait_queue);
} else {
mutex_unlock(&ca->remove_mutex);
}
return err;
}
@ -1893,6 +1919,7 @@ int dvb_ca_en50221_init(struct dvb_adapter *dvb_adapter,
}
mutex_init(&ca->ioctl_mutex);
mutex_init(&ca->remove_mutex);
if (signal_pending(current)) {
ret = -EINTR;
@ -1935,6 +1962,14 @@ void dvb_ca_en50221_release(struct dvb_ca_en50221 *pubca)
dprintk("%s\n", __func__);
mutex_lock(&ca->remove_mutex);
ca->exit = 1;
mutex_unlock(&ca->remove_mutex);
if (ca->dvbdev->users < 1)
wait_event(ca->dvbdev->wait_queue,
ca->dvbdev->users == 1);
/* shutdown the thread if there was one */
kthread_stop(ca->thread);