tty: serial: uartlite: register uart driver in init

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: tty: serial: uartlite: register uart driver in init When two instances of uart devices are probing, a concurrency race can occur. If one thread calls uart_register_driver function, which first allocates and assigns memory to 'uart_state' member of uart_driver structure, the other instance can bypass uart driver registration and call ulite_assign. This calls uart_add_one_port, which expects the uart driver to be fully initialized. This leads to a kernel panic due to a null pointer dereference: [ 8.143581] BUG: kernel NULL pointer dereference, address: 00000000000002b8 [ 8.156982] #PF: supervisor write access in kernel mode [ 8.156984] #PF: error_code(0x0002) - not-present page [ 8.156986] PGD 0 P4D 0 ... [ 8.180668] RIP: 0010:mutex_lock+0x19/0x30 [ 8.188624] Call Trace: [ 8.188629] ? __die_body.cold+0x1a/0x1f [ 8.195260] ? page_fault_oops+0x15c/0x290 [ 8.209183] ? __irq_resolve_mapping+0x47/0x80 [ 8.209187] ? exc_page_fault+0x64/0x140 [ 8.209190] ? asm_exc_page_fault+0x22/0x30 [ 8.209196] ? mutex_lock+0x19/0x30 [ 8.223116] uart_add_one_port+0x60/0x440 [ 8.223122] ? proc_tty_register_driver+0x43/0x50 [ 8.223126] ? tty_register_driver+0x1ca/0x1e0 [ 8.246250] ulite_probe+0x357/0x4b0 [uartlite] To prevent it, move uart driver registration in to init function. This will ensure that uart_driver is always registered when probe function is called.

References

• https://git.kernel.org/stable/c/5015eed450005bab6e5cb6810f7a62eab0434fc4
• https://git.kernel.org/stable/c/9c905fdbba68a6d73d39a6b7de9b9f0d6c46df87
• https://git.kernel.org/stable/c/6db06aaea07bb7c8e33a425cf7b98bf29ee6056e
• https://git.kernel.org/stable/c/8e958d10dd0ce5ae674cce460db5c9ca3f25243b
• https://git.kernel.org/stable/c/685d29f2c5057b32c7b1b46f2a7d303b926c8f72
• https://git.kernel.org/stable/c/f5e4229d94792b40e750f30c92bcf7a3107c72ef
• https://git.kernel.org/stable/c/6bd697b5fc39fd24e2aa418c7b7d14469f550a93