This bug is triggered during "os-prober" when it finds an active swap partition. At least, this is what is visible in the syslog.

The kernel log shows this:

[61932.439623] general protection fault: 0000 [#1] SMP 
[61932.439644] Modules linked in: btrfs xor raid6_pq ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c uas usb_storage pci_stub vboxpci(OE) vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) bnep rfcomm bluetooth nls_iso8859_1 intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm serio_raw lpc_ich snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic 8250_fintek tpm_infineon snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi mac_hid intel_smartconnect snd_seq snd_seq_device snd_timer snd mei_me mei shpchp soundcore parport_pc ppdev lp parport dm_crypt netconsole configfs hid_generic usbhid hid mxm_wmi crct10dif_pclmul crc32_pclmul ghash_clmulni_intel i915 aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper i2c_algo_bit cryptd drm_kms_helper drm ahci r8169 libahci mii wmi video
[61932.439979] CPU: 3 PID: 22789 Comm: cat Tainted: G        W  OE  3.19.0-26-generic #28~14.04.1-Ubuntu
[61932.440001] Hardware name: MSI MS-7817/CSM-B85M-E45 (MS-7817), BIOS V10.9 04/21/2015
[61932.440019] task: ffff88012a7c13a0 ti: ffff8800c7cfc000 task.ti: ffff8800c7cfc000
[61932.440097] RIP: 0010:[<ffffffff8106eebc>]  [<ffffffff8106eebc>] efi_call+0x7c/0x100
[61932.440118] RSP: 0018:ffff8800c7cffc60  EFLAGS: 00010002
[61932.440131] RAX: 0000000000000001 RBX: 0000000000000092 RCX: ffff8802116c7000
[61932.440148] RDX: ffff8802116c7400 RSI: ffff8802116c7000 RDI: 2d78756e696c2f63
[61932.440164] RBP: ffff8800c7cffd48 R08: ffff8802116c7820 R09: ffff8802116c7410
[61932.440181] R10: 0000000000001000 R11: 0000000000000246 R12: ffff8802116c7000
[61932.440197] R13: ffff8802116c7400 R14: ffff8802116c7820 R15: 000000000009a000
[61932.440214] FS:  00007ffa57bf6740(0000) GS:ffff88021eb80000(0000) knlGS:0000000000000000
[61932.440233] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[61932.440246] CR2: 0000000001a95038 CR3: 000000000009a000 CR4: 00000000001407e0
[61932.440263] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[61932.440279] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[61932.440295] Stack:
[61932.440300]  0000000000000001 000001c100000000 ffff88012a7c13a0 ffff88021edf7e08
[61932.440321]  ffff8802116c7418 0000000000000001 ffff8800c7cffd00 0000000080050033
[61932.440341]  0000000000000000 0000000000000000 00007ffeca3a3880 00007ffa57664bac
[61932.440360] Call Trace:
[61932.440370]  [<ffffffff81669558>] ? virt_efi_get_variable+0x68/0xa0
[61932.440386]  [<ffffffff81665b08>] efivar_entry_get+0x48/0xb0
[61932.440400]  [<ffffffff8166678a>] efivar_data_read+0x4a/0x90
[61932.440414]  [<ffffffff81666c06>] efivar_attr_show+0x46/0x70
[61932.440430]  [<ffffffff81264dfc>] sysfs_kf_seq_show+0xcc/0x1e0
[61932.440445]  [<ffffffff812633f3>] kernfs_seq_show+0x23/0x30
[61932.440459]  [<ffffffff8121029a>] seq_read+0xea/0x370
[61932.440472]  [<ffffffff81263bd5>] kernfs_fop_read+0x105/0x170
[61932.440487]  [<ffffffff811ecdd8>] __vfs_read+0x18/0x50
[61932.440500]  [<ffffffff811ece96>] vfs_read+0x86/0x140
[61932.440513]  [<ffffffff811ecf96>] SyS_read+0x46/0xb0
[61932.440527]  [<ffffffff817b688d>] system_call_fastpath+0x16/0x1b
[61932.440541] Code: 89 c8 48 89 f1 80 3d 3b 3d bd 00 00 74 1d 4c 89 3d 1a 3d bd 00 41 0f 20 df 4c 89 3d 17 3d bd 00 4c 8b 3d 18 3d bd 00 41 0f 22 df <ff> d7 80 3d 13 3d bd 00 00 74 41 4c 8b 3d fa 3c bd 00 41 0f 22 
[61932.440799] RIP  [<ffffffff8106eebc>] efi_call+0x7c/0x100
[61932.440813]  RSP <ffff8800c7cffc60>
[61932.446826] ---[ end trace ff309deb951e1b78 ]---

after which the machine is frozen, but still accessible via network (SSH) for some time but cannot be cleanly shutdown or rebooted.

The backtrace does seem to hint towards EFI functions. Does this bug need to be reassigned to another package?