In the Linux kernel, the following vulnerability has been resolved: usb: musb: sunxi: Fix accessing an released usb phy Commit 6ed05c68cbca ("usb: musb: sunxi: Explicitly release USB PHY on exit") will cause that usb phy @glue->xceiv is accessed after released. 1) register platform driver @sunxi_musb_driver // get the usb phy @glue->xceiv sunxi_musb_probe() -> devm_usb_get_phy(). 2) register and unregister platform driver @musb_driver musb_probe() -> sunxi_musb_init() use the phy here //the phy is released here musb_remove() -> sunxi_musb_exit() -> devm_usb_put_phy() 3) register @musb_driver again musb_probe() -> sunxi_musb_init() use the phy here but the phy has been released at 2). ... Fixed by reverting the commit, namely, removing devm_usb_put_phy() from sunxi_musb_exit().
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.