[PATCH 6.0 0707/1073] usb: gadget: f_hid: fix f_hidg lifetime vs cdev

Greg Kroah-Hartman
2022-12-28T16:24:04Z

From: John Keeping <john@metanate.com>

[ Upstream commit 89ff3dfac604614287ad5aad9370c3f984ea3f4b ]

The embedded struct cdev does not have its lifetime correctly tied to
the enclosing struct f_hidg, so there is a use-after-free if /dev/hidgN
is held open while the gadget is deleted.

This can readily be replicated with libusbgx's example programs (for
conciseness - operating directly via configfs is equivalent):

gadget-hid
exec 3<> /dev/hidg0
gadget-vid-pid-remove
exec 3<&-

Pull the existing device up in to struct f_hidg and make use of the
cdev_device_{add,del}() helpers. This changes the lifetime of the
device object to match struct f_hidg, but note that it is still added
and deleted at the same time.

Fixes: 71adf1189469 ("USB: gadget: add HID gadget driver")
Tested-by: Lee Jones <lee@kernel.org>
Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Reviewed-by: Lee Jones <lee@kernel.org>
Signed-off-by: John Keeping <john@metanate.com>
Link: https://lore.kernel.org/r/20221122123523.3068034-2-john@metanate.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/usb/gadget/function/f_hid.c | 52 ++++++++++++++++-------------
1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
index ca0a7d9eaa34..8b8bbeaa27cb 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -71,7 +71,7 @@ struct f_hidg {
wait_queue_head_t write_queue;
struct usb_request *req;

- int minor;
+ struct device dev;
struct cdev cdev;
struct usb_function func;

@@ -84,6 +84,14 @@ static inline struct f_hidg *func_to_hidg(struct usb_function *f)
return container_of(f, struct f_hidg, func);
}

+static void hidg_release(struct device *dev)
+{
+ struct f_hidg *hidg = container_of(dev, struct f_hidg, dev);
+
+ kfree(hidg->set_report_buf);
+ kfree(hidg);
+}
+
/*-------------------------------------------------------------------------*/
/* Static descriptors */

@@ -904,9 +912,7 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
struct usb_ep *ep;
struct f_hidg *hidg = func_to_hidg(f);
struct usb_string *us;
- struct device *device;
int status;
- dev_t dev;

/* maybe allocate device-global string IDs, and patch descriptors */
us = usb_gstrings_attach(c->cdev, ct_func_strings,
@@ -999,21 +1005,11 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)

/* create char device */
cdev_init(&hidg->cdev, &f_hidg_fops);
- dev = MKDEV(major, hidg->minor);
- status = cdev_add(&hidg->cdev, dev, 1);
+ status = cdev_device_add(&hidg->cdev, &hidg->dev);
if (status)
goto fail_free_descs;

- device = device_create(hidg_class, NULL, dev, NULL,
- "%s%d", "hidg", hidg->minor);
- if (IS_ERR(device)) {
- status = PTR_ERR(device);
- goto del;
- }
-
return 0;
-del:
- cdev_del(&hidg->cdev);
fail_free_descs:
usb_free_all_descriptors(f);
fail:
@@ -1244,9 +1240,7 @@ static void hidg_free(struct usb_function *f)

hidg = func_to_hidg(f);
opts = container_of(f->fi, struct f_hid_opts, func_inst);
- kfree(hidg->report_desc);
- kfree(hidg->set_report_buf);
- kfree(hidg);
+ put_device(&hidg->dev);
mutex_lock(&opts->lock);
--opts->refcnt;
mutex_unlock(&opts->lock);
@@ -1256,8 +1250,7 @@ static void hidg_unbind(struct usb_configuration *c, struct usb_function *f)
{
struct f_hidg *hidg = func_to_hidg(f);

- device_destroy(hidg_class, MKDEV(major, hidg->minor));
- cdev_del(&hidg->cdev);
+ cdev_device_del(&hidg->cdev, &hidg->dev);

usb_free_all_descriptors(f);
}
@@ -1266,6 +1259,7 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
{
struct f_hidg *hidg;
struct f_hid_opts *opts;
+ int ret;

/* allocate and initialize one new instance */
hidg = kzalloc(sizeof(*hidg), GFP_KERNEL);
@@ -1277,17 +1271,27 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
mutex_lock(&opts->lock);
++opts->refcnt;

- hidg->minor = opts->minor;
+ device_initialize(&hidg->dev);
+ hidg->dev.release = hidg_release;
+ hidg->dev.class = hidg_class;
+ hidg->dev.devt = MKDEV(major, opts->minor);
+ ret = dev_set_name(&hidg->dev, "hidg%d", opts->minor);
+ if (ret) {
+ --opts->refcnt;
+ mutex_unlock(&opts->lock);
+ return ERR_PTR(ret);
+ }
+
hidg->bInterfaceSubClass = opts->subclass;
hidg->bInterfaceProtocol = opts->protocol;
hidg->report_length = opts->report_length;
hidg->report_desc_length = opts->report_desc_length;
if (opts->report_desc) {
- hidg->report_desc = kmemdup(opts->report_desc,
- opts->report_desc_length,
- GFP_KERNEL);
+ hidg->report_desc = devm_kmemdup(&hidg->dev, opts->report_desc,
+ opts->report_desc_length,
+ GFP_KERNEL);
if (!hidg->report_desc) {
- kfree(hidg);
+ put_device(&hidg->dev);
mutex_unlock(&opts->lock);
return ERR_PTR(-ENOMEM);
}
--
2.35.1