After commit 415b43bdb008 "tty: serial: uartlite: Move uart register to probe", calling uart_unregister_driver unconditionally will trigger a null pointer dereference due to ulite_uart_driver may not registed. CPU: 1 PID: 3755 Comm: syz-executor.0 Not tainted 5.1.0+ #28 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xa9/0x10e lib/dump_stack.c:113 __kasan_report+0x171/0x18d mm/kasan/report.c:321 kasan_report+0xe/0x20 mm/kasan/common.c:614 tty_unregister_driver+0x19/0x100 drivers/tty/tty_io.c:3383 uart_unregister_driver+0x30/0xc0 drivers/tty/serial/serial_core.c:2579 __do_sys_delete_module kernel/module.c:1027 [inline] __se_sys_delete_module kernel/module.c:970 [inline] __x64_sys_delete_module+0x244/0x330 kernel/module.c:970 do_syscall_64+0x72/0x2a0 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe Call uart_unregister_driver only if ulite_uart_driver.state not null to fix it. Cc: Peter Korsgaard <jacmet@xxxxxxxxxx> Cc: Shubhrajyoti Datta <shubhrajyoti.datta@xxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Reported-by: Hulk Robot <hulkci@xxxxxxxxxx> Fixes: 415b43bdb008 ("tty: serial: uartlite: Move uart register to probe") Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> --- drivers/tty/serial/uartlite.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/uartlite.c b/drivers/tty/serial/uartlite.c index b8b912b5a8b9..06e79c11141d 100644 --- a/drivers/tty/serial/uartlite.c +++ b/drivers/tty/serial/uartlite.c @@ -897,7 +897,8 @@ static int __init ulite_init(void) static void __exit ulite_exit(void) { platform_driver_unregister(&ulite_platform_driver); - uart_unregister_driver(&ulite_uart_driver); + if (ulite_uart_driver.state) + uart_unregister_driver(&ulite_uart_driver); } module_init(ulite_init); -- 2.20.1