RHEL7: NULL pointer dereference occurs in hrtimer_active() which is called by destroy_cfs_bandwidth()

Issue

• kernel crash due to a NULL pointer dereference at hrtimer_active+0x2d:

crash> bt
PID: 30241  TASK: ffff8f087e5f8000  CPU: 1   COMMAND: "runc:[2:INIT]"
 #0 [ffff8f1deedb7ad0] machine_kexec at ffffffff99465754
 #1 [ffff8f1deedb7b30] __crash_kexec at ffffffff995209a2
 #2 [ffff8f1deedb7c00] crash_kexec at ffffffff99520a90
 #3 [ffff8f1deedb7c18] oops_end at ffffffff99b83778
 #4 [ffff8f1deedb7c40] no_context at ffffffff99474ad4
 #5 [ffff8f1deedb7c90] __bad_area_nosemaphore at ffffffff99474da2
 #6 [ffff8f1deedb7ce0] bad_area_nosemaphore at ffffffff99474ec4
 #7 [ffff8f1deedb7cf0] __do_page_fault at ffffffff99b86730
 #8 [ffff8f1deedb7d60] do_page_fault at ffffffff99b86955
 #9 [ffff8f1deedb7d90] page_fault at ffffffff99b82768
    [exception RIP: hrtimer_active+0x2d]
    RIP: ffffffff994c897d  RSP: ffff8f1deedb7e40  RFLAGS: 00010246
    RAX: 0000000000000000  RBX: ffff8f087e6a0180  RCX: 0000000000000003
    RDX: 0000000000000000  RSI: 0000000000000000  RDI: ffff8f087e6a0180
    RBP: ffff8f1deedb7e40   R8: ffffffff9a15cfc8   R9: 3a7362616c73203a
    R10: ffff8f1ad8cf8300  R11: 7266202c3233203a  R12: ffff8f087e6a0000
    R13: 00000000ffffffff  R14: 0000000000000000  R15: 0000000000000000
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
#10 [ffff8f1deedb7e48] hrtimer_try_to_cancel at ffffffff994c9659
#11 [ffff8f1deedb7e80] hrtimer_cancel at ffffffff994c976a
#12 [ffff8f1deedb7e98] free_fair_sched_group at ffffffff994e90a5
#13 [ffff8f1deedb7ec8] free_sched_group at ffffffff994d2ad2
#14 [ffff8f1deedb7ee0] sched_create_group at ffffffff994dc6cb
#15 [ffff8f1deedb7f00] sched_autogroup_create_attach at ffffffff994f04ff
#16 [ffff8f1deedb7f28] sys_setsid at ffffffff994b7bd3
#17 [ffff8f1deedb7f50] system_call_fastpath at ffffffff99b8bede
    RIP: 00007f4564bd9ae7  RSP: 00007ffd97409898  RFLAGS: 00010202
    RAX: 0000000000000070  RBX: 000055a1a04aa02c  RCX: 00007f4565130700
    RDX: 0000000000000004  RSI: 00007ffd9740991c  RDI: 0000000000000008
    RBP: 0000000000000000   R8: 0000000000000044   R9: 0000000000000000
    R10: 00007ffd97408ca0  R11: 0000000000000202  R12: 0000000000000000
    R13: 0000000000000000  R14: 0000000000000000  R15: 000000006c020000
    ORIG_RAX: 0000000000000070  CS: 0033  SS: 002b