"value":"In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: u_serial: Fix the issue that gs_start_io crashed due to accessing null pointer\n\nConsidering that in some extreme cases,\nwhen u_serial driver is accessed by multiple threads,\nThread A is executing the open operation and calling the gs_open,\nThread B is executing the disconnect operation and calling the\ngserial_disconnect function,The port->port_usb pointer will be set to NULL.\n\nE.g.\n Thread A Thread B\n gs_open() gadget_unbind_driver()\n gs_start_io() composite_disconnect()\n gs_start_rx() gserial_disconnect()\n ... ...\n spin_unlock(&port->port_lock)\n status = usb_ep_queue() spin_lock(&port->port_lock)\n spin_lock(&port->port_lock) port->port_usb = NULL\n gs_free_requests(port->port_usb->in) spin_unlock(&port->port_lock)\n Crash\n\nThis causes thread A to access a null pointer (port->port_usb is null)\nwhen calling the gs_free_requests function, causing a crash.\n\nIf port_usb is NULL, the release request will be skipped as it\nwill be done by gserial_disconnect.\n\nSo add a null pointer check to gs_start_io before attempting\nto access the value of the pointer port->port_usb.\n\nCall trace:\n gs_start_io+0x164/0x25c\n gs_open+0x108/0x13c\n tty_open+0x314/0x638\n chrdev_open+0x1b8/0x258\n do_dentry_open+0x2c4/0x700\n vfs_open+0x2c/0x3c\n path_openat+0xa64/0xc60\n do_filp_open+0xb8/0x164\n do_sys_openat2+0x84/0xf0\n __arm64_sys_openat+0x70/0x9c\n invoke_syscall+0x58/0x114\n el0_svc_common+0x80/0xe0\n do_el0_svc+0x1c/0x28\n el0_svc+0x38/0x68"