comedi: runflags cannot determine whether to reclaim chanlist

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

comedi: runflags cannot determine whether to reclaim chanlist

syzbot reported a memory leak [1], because commit 4e1da516debb ("comedi:

Add reference counting for Comedi command handling") did not consider

the exceptional exit case in do_cmd_ioctl() where runflags is not set.

This caused chanlist not to be properly freed by do_become_nonbusy(),

as it only frees chanlist when runflags is correctly set.

Added a check in do_become_nonbusy() for the case where runflags is not

set, to properly free the chanlist memory.

[1]

BUG: memory leak

backtrace (crc 844a0efa):

__comedi_get_user_chanlist drivers/comedi/comedi_fops.c:1815 [inline]

do_cmd_ioctl.part.0+0x112/0x350 drivers/comedi/comedi_fops.c:1890

do_cmd_ioctl drivers/comedi/comedi_fops.c:1858 [inline]