Messages in this thread | | | Subject | [PATCH] USB: gadget: Fix use-after-free during usb config switch | From | jiantao zhang <> | Date | Wed, 9 Nov 2022 22:11:51 +0800 |
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> In the process of switching USB config from rndis to other config, > if function gadget->ops->pullup() return an error,it will inevitably > cause a system panic(use after free). > > Analysis as follows: > ===================================================================== > (1) write /config/usb_gadget/g1/UDC "none" (init.usb.configfs.rc:2) > > gether_disconnect+0x2c/0x1f8 (dev->port_usb = NULL) > rndis_disable+0x4c/0x74 > composite_disconnect+0x74/0xb0 > configfs_composite_disconnect+0x60/0x7c > usb_gadget_disconnect+0x70/0x124 > usb_gadget_unregister_driver+0xc8/0x1d8 > gadget_dev_desc_UDC_store+0xec/0x1e4 > > In general, pointer dev->port will be set to null. > In function usb_gadget_disconnect(),gadget->udc->driver->disconnect() > will not be called when gadget->ops->pullup() return an error, therefore, > pointer dev->port will not be set to NULL. > If pointer dev->port_usb is not null, it will cause an exception of using > the freed memory in step3. > > (2) rm /config/usb_gadget/g1/configs/b.1/f1 (init.usb.configfs.rc:8) > (f1 -> ../../../../usb_gadget/g1/functions/rndis.gs4) > > rndis_deregister+0x28/0x54 (kfree(params)) > rndis_free+0x44/0x7c (kfree(rndis)) > usb_put_function+0x14/0x1c > config_usb_cfg_unlink+0xc4/0xe0 > configfs_unlink+0x124/0x1c8 > vfs_unlink+0x114/0x1dc > > (3) rmdir /config/usb_gadget/g1/functions/rndis.gs4 > (init.usb.configfs.rc:11) > > Call trace: > panic+0x1fc/0x3d0 > die+0x29c/0x2a8 > die_kernel_fault+0x60/0x90 > do_page_fault+0xa8/0x46c > do_mem_abort+0x3c/0xac > el1_abort+0x3c/0x58 > el1_sync_handler+0x40/0x78 > el1_sync+0x84/0x140 > 0xffffff801138f880 (params->resp_avail is an illegal function pointer) > rndis_close+0x28/0x34 (->rndis_indicate_status_msg-> params->resp_avail()) > eth_stop+0x74/0x110 (if dev->port_usb != NULL, call rndis_close) > __dev_close_many+0x134/0x194 > dev_close_many+0x48/0x194 > rollback_registered_many+0x118/0x814 > unregister_netdevice_queue+0xe0/0x168 > unregister_netdev+0x20/0x30 > gether_cleanup+0x1c/0x38 > rndis_free_inst+0x2c/0x58 > usb_put_function_instance+0x20/0x34 > rndis_attr_release+0xc/0x14 > kref_put+0x74/0xb8 > config_item_put+0x14/0x1c > configfs_rmdir+0x314/0x374 > vfs_rmdir+0xa4/0x15c > > In step3,function pointer params->resp_avail() is a wild pointer > becase pointer params has been freed in step2. > > Free mem stack(in step2): > usb_put_function -> rndis_free -> rndis_deregister -> kfree(params) > > use-after-free stack(in step3): > eth_stop -> rndis_close -> rndis_signal_disconnect -> > rndis_indicate_status_msg -> params->resp_avail() > > In function eth_stop(), if pointer dev->port_usb is NULL, function > rndis_close() will not be called. > > If gadget->ops->pullup() return an error in step),dev->port_usb will > not be set to null. So, a panic will be caused in step3. > ======================================================================= > > Through above analysis, i think gadget->udc->driver->disconnect() need > to be called even if gadget->udc->driver->disconnect() return an error. > > This reverts commit 0a55187a1ec8c03d0619e7ce41d10fdc39cff036 > > I think this change is a code optimization, not a solution to specific > problem. And i think this problem is caused by this change,revert it can > solve this problem. > > Of course, my understanding may be inaccurate.There may be a better > solution to this problem. If possible, please give some suggestions, > thanks. > > Fixes:<0a55187a1ec8c> (USB: gadget core: Issue ->disconnect() > callback from usb_gadget_disconnect()) > > Signed-off-by: Jiantao Zhang <water.zhangjiantao@huawei.com> > Signed-off-by: TaoXue <xuetao09@huawei.com> > --- > drivers/usb/gadget/udc/core.c | 20 +++++++++++--------- > 1 file changed, 11 insertions(+), 9 deletions(-) > > diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c > index c63c0c2cf649..b502b2ac4824 100644 > --- a/drivers/usb/gadget/udc/core.c > +++ b/drivers/usb/gadget/udc/core.c > @@ -707,9 +707,6 @@ EXPORT_SYMBOL_GPL(usb_gadget_connect); > * as a disconnect (when a VBUS session is active). Not all systems > * support software pullup controls. > * > - * Following a successful disconnect, invoke the ->disconnect() callback > - * for the current gadget driver so that UDC drivers don't need to. > - * > * Returns zero on success, else negative errno. > */ > int usb_gadget_disconnect(struct usb_gadget *gadget) > @@ -734,13 +731,8 @@ int usb_gadget_disconnect(struct usb_gadget *gadget) > } > > ret = gadget->ops->pullup(gadget, 0); > - if (!ret) { > + if (!ret) > gadget->connected = 0; > - mutex_lock(&udc_lock); > - if (gadget->udc->driver) > - gadget->udc->driver->disconnect(gadget); > - mutex_unlock(&udc_lock); > - } > > out: > trace_usb_gadget_disconnect(gadget, ret); > @@ -1532,6 +1524,11 @@ static void gadget_unbind_driver(struct device *dev) > kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE); > > usb_gadget_disconnect(gadget); > + > + mutex_lock(&udc_lock); > + udc->driver->disconnect(udc->gadget); > + mutex_unlock(&udc_lock); > + > usb_gadget_disable_async_callbacks(udc); > if (gadget->irq) > synchronize_irq(gadget->irq); > @@ -1626,6 +1623,11 @@ static ssize_t soft_connect_store(struct device *dev, > usb_gadget_connect(udc->gadget); > } else if (sysfs_streq(buf, "disconnect")) { > usb_gadget_disconnect(udc->gadget); > + > + mutex_lock(&udc_lock); > + udc->driver->disconnect(udc->gadget); > + mutex_unlock(&udc_lock); > + > usb_gadget_udc_stop(udc); > } else { > dev_err(dev, "unsupported command '%s'\n", buf);
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