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

serial: core: fix NULL pointer dereference in serial core unregister port()

port->port dev is NULL when no port device is installed: it is cleared on teardown, and never set if registration failed before serial core port device add(). serial core unregister port() passes it straight to serial core get ctrl dev(), which dereferences it:

KASAN: null-ptr-deref in range [0x0000000000000040-0x0000000000000047] RIP: serial core unregister port Call Trace: serial8250 unregister port serial8250 remove unbind store

Return early when there is no port device, and read port->port dev under port mutex.

Also clear port->port dev on the serial core register port() error path, where the port device has already been removed.