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  1. RHEL
  2. RHEL-18443

[Azure/HyperV] kernel panic in fb_videomode_to_var

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      What were you trying to do that didn't work?

      During a normal reboot an Azure Machine (HyperV) panicked with the following message:

      [ 1.591252] Console: switching to mono frame buffer device 128x48
      [ 1.591258] BUG: unable to handle kernel NULL pointer dereference at 000000000000000c
      [ 1.591259] PGD 0 P4D 0
      [ 1.591261] Oops: 0000 [#1] SMP NOPTI
      [ 1.591263] CPU: 6 PID: 86 Comm: kworker/6:1 Not tainted 4.18.0-513.9.1.el8_9.x86_64 #1
      [ 1.591265] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 07/12/2023
      [ 1.591267] Workqueue: events fbcon_register_existing_fbs
      [ 1.591272] RIP: 0010:fb_videomode_to_var+0x5/0x70
      [ 1.591275] Code: 9a 3b 31 d2 41 f7 f0 31 d2 69 c0 e8 03 00 00 f7 f6 31 d2 f7 f1 89 47 08 e9 18 a1 89 00 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <8b> 46 0c 89 07 8b 46 10 89 47 04 8b 46 0c 89 47 08 8b 46 10 48 c7
      [ 1.591277] RSP: 0018:ffffa5c806597c70 EFLAGS: 00010246
      [ 1.591278] RAX: 0000000000000000 RBX: ffffa5c806597ca8 RCX: 0000000000000000
      [ 1.591280] RDX: ffffa5c806597ca8 RSI: 0000000000000000 RDI: ffffa5c806597ca8
      [ 1.591281] RBP: ffffffffbd348c80 R08: ffffffffbb0633a0 R09: 7665642072656666
      [ 1.591282] R10: 756220656d613834 R11: 206f6e6f6d203834 R12: ffffffffbd348b20
      [ 1.591283] R13: ffffffffbb5c3a20 R14: ffff963d8061b400 R15: ffffffffbd348b20
      [ 1.591284] FS: 0000000000000000(0000) GS:ffff964c9fd80000(0000) knlGS:0000000000000000
      [ 1.591286] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      [ 1.591287] CR2: 000000000000000c CR3: 0000000160e60000 CR4: 0000000000350ee0
      [ 1.591290] Call Trace:
      [ 1.591293] ? __die_body+0x1a/0x60
      [ 1.591298] ? no_context+0x1ba/0x3f0
      [ 1.591300] ? selinux_kernfs_init_security+0x50/0x220
      [ 1.591303] ? __bad_area_nosemaphore+0x16c/0x1c0
      [ 1.591305] ? do_page_fault+0x37/0x130
      [ 1.591306] ? page_fault+0x1e/0x30
      [ 1.591310] ? fb_videomode_to_var+0x5/0x70
      [ 1.591311] display_to_var+0x16/0x90
      [ 1.591313] fbcon_switch+0x126/0x4d0
      [ 1.591315] redraw_screen+0x151/0x240
      [ 1.591319] do_bind_con_driver.cold.29+0xe1/0x10d
      [ 1.591322] do_take_over_console+0x113/0x190
      [ 1.591324] do_fbcon_takeover+0x5c/0xc0
      [ 1.591326] fbcon_register_existing_fbs+0x48/0x70
      [ 1.591328] process_one_work+0x1d3/0x390
      [ 1.591331] ? process_one_work+0x390/0x390
      [ 1.591333] worker_thread+0x30/0x390
      [ 1.591335] ? process_one_work+0x390/0x390
      [ 1.591337] kthread+0x134/0x150
      [ 1.591340] ? set_kthread_struct+0x50/0x50
      [ 1.591341] ret_from_fork+0x35/0x40
      [ 1.591346] Modules linked in: hv_netvsc(+) hv_storvsc hyperv_fb scsi_transport_fc hyperv_keyboard hid_hyperv hv_vmbus crc32c_intel dm_mirror dm_region_hash dm_log dm_mod fuse
      [ 1.591354] CR2: 000000000000000c
      [ 1.591355] ---[ end trace 46731358462834bb ]---
      [ 1.591356] RIP: 0010:fb_videomode_to_var+0x5/0x70
      [ 1.591358] Code: 9a 3b 31 d2 41 f7 f0 31 d2 69 c0 e8 03 00 00 f7 f6 31 d2 f7 f1 89 47 08 e9 18 a1 89 00 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <8b> 46 0c 89 07 8b 46 10 89 47 04 8b 46 0c 89 47 08 8b 46 10 48 c7
      [ 1.591359] RSP: 0018:ffffa5c806597c70 EFLAGS: 00010246
      [ 1.591360] RAX: 0000000000000000 RBX: ffffa5c806597ca8 RCX: 0000000000000000
      [ 1.591361] RDX: ffffa5c806597ca8 RSI: 0000000000000000 RDI: ffffa5c806597ca8
      [ 1.591362] RBP: ffffffffbd348c80 R08: ffffffffbb0633a0 R09: 7665642072656666
      [ 1.591363] R10: 756220656d613834 R11: 206f6e6f6d203834 R12: ffffffffbd348b20
      [ 1.591364] R13: ffffffffbb5c3a20 R14: ffff963d8061b400 R15: ffffffffbd348b20
      [ 1.591365] FS: 0000000000000000(0000) GS:ffff964c9fd80000(0000) knlGS:0000000000000000
      [ 1.591366] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      [ 1.591367] CR2: 000000000000000c CR3: 0000000160e60000 CR4: 0000000000350ee0
      [ 1.591368] Kernel panic - not syncing: Fatal exception
      [ 1.592441] Kernel Offset: 0x38600000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
      

       

      Please provide the package NVR for which bug is seen:

      kernel-4.18.0-513.9.1.el8_9.x86_64

      How reproducible:

      Does not always happen, happens during boot

      Steps to reproduce

      1. systemctl reboot
      2.  
      3.  

      Expected results

      Boots fine

      Actual results

      hanging boot

      Additional Info: Support Case 03684278

      looks a bit like this old case:

      https://bugzilla.redhat.com/show_bug.cgi?id=2030995

              jfalempe@redhat.com Jocelyn Falempe
              demtekaa Klaas Demter
              Stephen Tweedie
              xgl-maint xgl-maint
              Xiaoqiang Xiong Xiaoqiang Xiong
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                Created:
                Updated: