[PATCH 4.19 086/148] media: dvb-core: Fix use-after-free due to race at dvb_register_device()

Sasha Levin
2024-03-24T23:51:55Z

From: Hyunwoo Kim <imv4bel@gmail.com>

[ Upstream commit 627bb528b086b4136315c25d6a447a98ea9448d3 ]

dvb_register_device() dynamically allocates fops with kmemdup()
to set the fops->owner.
And these fops are registered in 'file->f_ops' using replace_fops()
in the dvb_device_open() process, and kfree()d in dvb_free_device().

However, it is not common to use dynamically allocated fops instead
of 'static const' fops as an argument of replace_fops(),
and UAF may occur.
These UAFs can occur on any dvb type using dvb_register_device(),
such as dvb_dvr, dvb_demux, dvb_frontend, dvb_net, etc.

So, instead of kfree() the fops dynamically allocated in
dvb_register_device() in dvb_free_device() called during the
.disconnect() process, kfree() it collectively in exit_dvbdev()
called when the dvbdev.c module is removed.

Link: https://lore.kernel.org/linux-media/20221117045925.14297-4-imv4bel@gmail.com
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Stable-dep-of: 8c64f4cdf4e6 ("media: edia: dvbdev: fix a use-after-free")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/dvb-core/dvbdev.c | 84 ++++++++++++++++++++++++---------
include/media/dvbdev.h | 15 ++++++
2 files changed, 78 insertions(+), 21 deletions(-)

diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
index cf0c428f5776b..35c272d77375e 100644
--- a/drivers/media/dvb-core/dvbdev.c
+++ b/drivers/media/dvb-core/dvbdev.c
@@ -37,6 +37,7 @@
#include <media/tuner.h>

static DEFINE_MUTEX(dvbdev_mutex);
+static LIST_HEAD(dvbdevfops_list);
static int dvbdev_debug;

module_param(dvbdev_debug, int, 0644);
@@ -464,14 +465,15 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
enum dvb_device_type type, int demux_sink_pads)
{
struct dvb_device *dvbdev;
- struct file_operations *dvbdevfops;
+ struct file_operations *dvbdevfops = NULL;
+ struct dvbdevfops_node *node = NULL, *new_node = NULL;
struct device *clsdev;
int minor;
int id, ret;

mutex_lock(&dvbdev_register_lock);

- if ((id = dvbdev_get_free_id (adap, type)) < 0){
+ if ((id = dvbdev_get_free_id (adap, type)) < 0) {
mutex_unlock(&dvbdev_register_lock);
*pdvbdev = NULL;
pr_err("%s: couldn't find free device id\n", __func__);
@@ -479,18 +481,45 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
}

*pdvbdev = dvbdev = kzalloc(sizeof(*dvbdev), GFP_KERNEL);
-
if (!dvbdev){
mutex_unlock(&dvbdev_register_lock);
return -ENOMEM;
}

- dvbdevfops = kmemdup(template->fops, sizeof(*dvbdevfops), GFP_KERNEL);
+ /*
+ * When a device of the same type is probe()d more than once,
+ * the first allocated fops are used. This prevents memory leaks
+ * that can occur when the same device is probe()d repeatedly.
+ */
+ list_for_each_entry(node, &dvbdevfops_list, list_head) {
+ if (node->fops->owner == adap->module &&
+ node->type == type &&
+ node->template == template) {
+ dvbdevfops = node->fops;
+ break;
+ }
+ }

- if (!dvbdevfops){
- kfree (dvbdev);
- mutex_unlock(&dvbdev_register_lock);
- return -ENOMEM;
+ if (dvbdevfops == NULL) {
+ dvbdevfops = kmemdup(template->fops, sizeof(*dvbdevfops), GFP_KERNEL);
+ if (!dvbdevfops) {
+ kfree(dvbdev);
+ mutex_unlock(&dvbdev_register_lock);
+ return -ENOMEM;
+ }
+
+ new_node = kzalloc(sizeof(struct dvbdevfops_node), GFP_KERNEL);
+ if (!new_node) {
+ kfree(dvbdevfops);
+ kfree(dvbdev);
+ mutex_unlock(&dvbdev_register_lock);
+ return -ENOMEM;
+ }
+
+ new_node->fops = dvbdevfops;
+ new_node->type = type;
+ new_node->template = template;
+ list_add_tail (&new_node->list_head, &dvbdevfops_list);
}

memcpy(dvbdev, template, sizeof(struct dvb_device));
@@ -501,20 +530,20 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
dvbdev->priv = priv;
dvbdev->fops = dvbdevfops;
init_waitqueue_head (&dvbdev->wait_queue);
-
dvbdevfops->owner = adap->module;
-
list_add_tail (&dvbdev->list_head, &adap->device_list);
-
down_write(&minor_rwsem);
#ifdef CONFIG_DVB_DYNAMIC_MINORS
for (minor = 0; minor < MAX_DVB_MINORS; minor++)
if (dvb_minors[minor] == NULL)
break;
-
if (minor == MAX_DVB_MINORS) {
+ if (new_node) {
+ list_del (&new_node->list_head);
+ kfree(dvbdevfops);
+ kfree(new_node);
+ }
list_del (&dvbdev->list_head);
- kfree(dvbdevfops);
kfree(dvbdev);
up_write(&minor_rwsem);
mutex_unlock(&dvbdev_register_lock);
@@ -523,41 +552,47 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
#else
minor = nums2minor(adap->num, type, id);
#endif
-
dvbdev->minor = minor;
dvb_minors[minor] = dvb_device_get(dvbdev);
up_write(&minor_rwsem);
-
ret = dvb_register_media_device(dvbdev, type, minor, demux_sink_pads);
if (ret) {
pr_err("%s: dvb_register_media_device failed to create the mediagraph\n",
__func__);
-
+ if (new_node) {
+ list_del (&new_node->list_head);
+ kfree(dvbdevfops);
+ kfree(new_node);
+ }
dvb_media_device_free(dvbdev);
list_del (&dvbdev->list_head);
- kfree(dvbdevfops);
kfree(dvbdev);
mutex_unlock(&dvbdev_register_lock);
return ret;
}

- mutex_unlock(&dvbdev_register_lock);
-
clsdev = device_create(dvb_class, adap->device,
MKDEV(DVB_MAJOR, minor),
dvbdev, "dvb%d.%s%d", adap->num, dnames[type], id);
if (IS_ERR(clsdev)) {
pr_err("%s: failed to create device dvb%d.%s%d (%ld)\n",
__func__, adap->num, dnames[type], id, PTR_ERR(clsdev));
+ if (new_node) {
+ list_del (&new_node->list_head);
+ kfree(dvbdevfops);
+ kfree(new_node);
+ }
dvb_media_device_free(dvbdev);
list_del (&dvbdev->list_head);
- kfree(dvbdevfops);
kfree(dvbdev);
+ mutex_unlock(&dvbdev_register_lock);
return PTR_ERR(clsdev);
}
+
dprintk("DVB: register adapter%d/%s%d @ minor: %i (0x%02x)\n",
adap->num, dnames[type], id, minor, minor);

+ mutex_unlock(&dvbdev_register_lock);
return 0;
}
EXPORT_SYMBOL(dvb_register_device);
@@ -586,7 +621,6 @@ static void dvb_free_device(struct kref *ref)
{
struct dvb_device *dvbdev = container_of(ref, struct dvb_device, ref);

- kfree (dvbdev->fops);
kfree (dvbdev);
}

@@ -1082,9 +1116,17 @@ static int __init init_dvbdev(void)

static void __exit exit_dvbdev(void)
{
+ struct dvbdevfops_node *node, *next;
+
class_destroy(dvb_class);
cdev_del(&dvb_device_cdev);
unregister_chrdev_region(MKDEV(DVB_MAJOR, 0), MAX_DVB_MINORS);
+
+ list_for_each_entry_safe(node, next, &dvbdevfops_list, list_head) {
+ list_del (&node->list_head);
+ kfree(node->fops);
+ kfree(node);
+ }
}

subsys_initcall(init_dvbdev);
diff --git a/include/media/dvbdev.h b/include/media/dvbdev.h
index 09279ed0051ea..0e2bda5ccadd5 100644
--- a/include/media/dvbdev.h
+++ b/include/media/dvbdev.h
@@ -189,6 +189,21 @@ struct dvb_device {
void *priv;
};

+/**
+ * struct dvbdevfops_node - fops nodes registered in dvbdevfops_list
+ *
+ * @fops: Dynamically allocated fops for ->owner registration
+ * @type: type of dvb_device
+ * @template: dvb_device used for registration
+ * @list_head: list_head for dvbdevfops_list
+ */
+struct dvbdevfops_node {
+ struct file_operations *fops;
+ enum dvb_device_type type;
+ const struct dvb_device *template;
+ struct list_head list_head;
+};
+
/**
* dvb_device_get - Increase dvb_device reference
*
--
2.43.0