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author | Hyunwoo Kim <v4bel@theori.io> | 2022-11-21 06:33:08 +0000 |
---|---|---|
committer | Mauro Carvalho Chehab <mchehab@kernel.org> | 2023-05-14 16:04:48 +0100 |
commit | 280a8ab81733da8bc442253c700a52c4c0886ffd (patch) | |
tree | 8d296b8d536954eb9849cfceeef24951c6deed0d /drivers/media | |
parent | b8c75e4a1b325ea0a9433fa8834be97b5836b946 (diff) | |
download | linux-stable-280a8ab81733da8bc442253c700a52c4c0886ffd.tar.gz linux-stable-280a8ab81733da8bc442253c700a52c4c0886ffd.tar.bz2 linux-stable-280a8ab81733da8bc442253c700a52c4c0886ffd.zip |
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>
Diffstat (limited to 'drivers/media')
-rw-r--r-- | drivers/media/dvb-core/dvb_ca_en50221.c | 37 |
1 files changed, 36 insertions, 1 deletions
diff --git a/drivers/media/dvb-core/dvb_ca_en50221.c b/drivers/media/dvb-core/dvb_ca_en50221.c index b6ca29dfb184..baf64540dc00 100644 --- a/drivers/media/dvb-core/dvb_ca_en50221.c +++ b/drivers/media/dvb-core/dvb_ca_en50221.c @@ -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); |