On Tue, Apr 06, 2021 at 06:13:59PM +0530, Anirudh Rayabharam wrote: > Multiple ttys try to claim the same the minor number causing a double > unregistration of the same device. The first unregistration succeeds > but the next one results in a null-ptr-deref. > > The get_free_serial_index() function returns an available minor number > but doesn't assign it immediately. The assignment is done by the caller > later. But before this assignment, calls to get_free_serial_index() > would return the same minor number. > > Fix this by modifying get_free_serial_index to assign the minor number > immediately after one is found to be and rename it to obtain_minor() > to better reflect what it does. Similary, rename set_serial_by_index() > to release_minor() and modify it to free up the minor number of the > given hso_serial. Every obtain_minor() should have corresponding > release_minor() call. > > Reported-by: syzbot+c49fe6089f295a05e6f8@xxxxxxxxxxxxxxxxxxxxxxxxx > Tested-by: syzbot+c49fe6089f295a05e6f8@xxxxxxxxxxxxxxxxxxxxxxxxx > > Signed-off-by: Anirudh Rayabharam <mail@xxxxxxxxxxxxx> Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
