[PATCH openEuler-1.0-LTS] media: dvb-core: Fix use-after-free due to race condition at dvb_ca_en50221

From: Hyunwoo Kim v4bel@theori.io

mainline inclusion from mainline-v6.4-rc3 commit 280a8ab81733da8bc442253c700a52c4c0886ffd category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I63D3C CVE: CVE-2022-45919

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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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 Signed-off-by: ZhangPeng zhangpeng362@huawei.com --- drivers/media/dvb-core/dvb_ca_en50221.c | 37 ++++++++++++++++++++++++- 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/drivers/media/dvb-core/dvb_ca_en50221.c b/drivers/media/dvb-core/dvb_ca_en50221.c index 4d371cea0d5d..fe152007c963 100644 --- a/drivers/media/dvb-core/dvb_ca_en50221.c +++ b/drivers/media/dvb-core/dvb_ca_en50221.c @@ -162,6 +162,12 @@ 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) @@ -1717,12 +1723,22 @@ 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; }

@@ -1747,6 +1763,7 @@ 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; }

@@ -1766,6 +1783,8 @@ 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); @@ -1776,6 +1795,13 @@ 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; }

@@ -1900,6 +1926,7 @@ 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; @@ -1942,6 +1969,14 @@ 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);