In the Linux kernel, the following vulnerability has been resolved:

USB: gadget: Fix use-after-free during usb config switch

In the process of switching USB config from rndis to other config, if the hardware does not support the ->pullup callback, or the hardware encounters a low probability fault, both of them may cause the ->pullup callback to fail, which will then cause a system panic (use after free).

The gadget drivers sometimes need to be unloaded regardless of the hardwares behavior.

Analysis as follows:

(1) write /config/usb_gadget/g1/UDC none

gether_disconnect+0x2c/0x1f8 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

(2) rm /config/usb_gadget/g1/configs/b.1/f1

rndis_deregister+0x28/0x54 rndis_free+0x44/0x7c 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

panic+0x1fc/0x3d0 do_page_fault+0xa8/0x46c do_mem_abort+0x3c/0xac el1_sync_handler+0x40/0x78 0xffffff801138f880 rndis_close+0x28/0x34 eth_stop+0x74/0x110 dev_close_many+0x48/0x194 rollback_registered_many+0x118/0x814 unregister_netdev+0x20/0x30 gether_cleanup+0x1c/0x38 rndis_attr_release+0xc/0x14 kref_put+0x74/0xb8 configfs_rmdir+0x314/0x374

If gadget->ops->pullup() return an error, function rndis_close() will be called, then it will causes a use-after-free problem.

Affected Software

References

• https://git.kernel.org/stable/c/30e926aa835ac2e6ad05822e4cb75833feb0d99f
• https://git.kernel.org/stable/c/99a58ac42d9b6911834b0224b6782aea0c311346
• https://git.kernel.org/stable/c/afdc12887f2b2ecf20d065a7d81ad29824155083