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Message-ID: References: <0f8c0e27-e60d-4e64-bc8a-6cb407c67ab2@xen.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="uA3h3C1LK1Wh2sS5" Content-Disposition: inline In-Reply-To: --uA3h3C1LK1Wh2sS5 Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Wed, 23 Apr 2025 14:41:59 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Julien Grall Cc: xen-devel , Juergen Gross Subject: Re: NULL pointer dereference in xenbus_thread->... On Sat, Jun 01, 2024 at 12:48:33AM +0200, Marek Marczykowski-G=C3=B3recki w= rote: > On Tue, Mar 26, 2024 at 11:00:50AM +0000, Julien Grall wrote: > > Hi Marek, > >=20 > > +Juergen for visibility > >=20 > > When sending a bug report, I would suggest to CC relevant people as > > otherwise it can get lost (not may people monitors Xen devel if they ar= e not > > CCed). > >=20 > > Cheers, > >=20 > > On 25/03/2024 16:17, Marek Marczykowski-G=C3=B3recki wrote: > > > On Sun, Oct 22, 2023 at 04:14:30PM +0200, Marek Marczykowski-G=C3=B3r= ecki wrote: > > > > On Mon, Aug 28, 2023 at 11:50:36PM +0200, Marek Marczykowski-G=C3= =B3recki wrote: > > > > > Hi, > > > > >=20 > > > > > I've noticed in Qubes's CI failure like this: > > > > >=20 > > > > > [ 871.271292] BUG: kernel NULL pointer dereference, address: 000= 0000000000000 > > > > > [ 871.275290] #PF: supervisor read access in kernel mode > > > > > [ 871.277282] #PF: error_code(0x0000) - not-present page > > > > > [ 871.279182] PGD 106fdb067 P4D 106fdb067 PUD 106fdc067 PMD 0 > > > > > [ 871.281071] Oops: 0000 [#1] PREEMPT SMP NOPTI > > > > > [ 871.282698] CPU: 1 PID: 28 Comm: xenbus Not tainted 6.1.43-1.q= ubes.fc37.x86_64 #1 > > > > > [ 871.285222] Hardware name: QEMU Standard PC (i440FX + PIIX, 19= 96), BIOS rel-1.16.0-0-gd239552-rebuilt.opensuse.org 04/01/2014 > > > > > [ 871.288883] RIP: e030:__wake_up_common+0x4c/0x180 > > > > > [ 871.292838] Code: 24 0c 89 4c 24 08 4d 85 c9 74 0a 41 f6 01 04= 0f 85 a3 00 00 00 48 8b 43 08 4c 8d 40 e8 48 83 c3 08 49 8d 40 18 48 39 c3= 74 5b <49> 8b 40 18 31 ed 4c 8d 70 e8 45 8b 28 41 f6 c5 04 75 5f 49 8b 40 > > > > > [ 871.299776] RSP: e02b:ffffc900400f7e10 EFLAGS: 00010082 > > > > > [ 871.301656] RAX: 0000000000000000 RBX: ffff88810541ce98 RCX: 0= 000000000000000 > > > > > [ 871.304255] RDX: 0000000000000001 RSI: 0000000000000003 RDI: f= fff88810541ce90 > > > > > [ 871.306714] RBP: ffffc900400f0280 R08: ffffffffffffffe8 R09: f= fffc900400f7e68 > > > > > [ 871.309937] R10: 0000000000007ff0 R11: ffff888100ad3000 R12: f= fffc900400f7e68 > > > > > [ 871.312326] R13: 0000000000000000 R14: 0000000000000000 R15: 0= 000000000000000 > > > > > [ 871.314647] FS: 0000000000000000(0000) GS:ffff88813ff00000(00= 00) knlGS:0000000000000000 > > > > > [ 871.317677] CS: 10000e030 DS: 0000 ES: 0000 CR0: 000000008005= 0033 > > > > > [ 871.319644] CR2: 0000000000000000 CR3: 00000001067fe000 CR4: 0= 000000000040660 > > > > > [ 871.321973] Call Trace: > > > > > [ 871.322782] > > > > > [ 871.323494] ? show_trace_log_lvl+0x1d3/0x2ef > > > > > [ 871.324901] ? show_trace_log_lvl+0x1d3/0x2ef > > > > > [ 871.326310] ? show_trace_log_lvl+0x1d3/0x2ef > > > > > [ 871.327721] ? __wake_up_common_lock+0x82/0xd0 > > > > > [ 871.329147] ? __die_body.cold+0x8/0xd > > > > > [ 871.330378] ? page_fault_oops+0x163/0x1a0 > > > > > [ 871.331691] ? exc_page_fault+0x70/0x170 > > > > > [ 871.332946] ? asm_exc_page_fault+0x22/0x30 > > > > > [ 871.334454] ? __wake_up_common+0x4c/0x180 > > > > > [ 871.335777] __wake_up_common_lock+0x82/0xd0 > > > > > [ 871.337183] ? process_writes+0x240/0x240 > > > > > [ 871.338461] process_msg+0x18e/0x2f0 > > > > > [ 871.339627] xenbus_thread+0x165/0x1c0 > > > > > [ 871.340830] ? cpuusage_read+0x10/0x10 > > > > > [ 871.342032] kthread+0xe9/0x110 > > > > > [ 871.343317] ? kthread_complete_and_exit+0x20/0x20 > > > > > [ 871.345020] ret_from_fork+0x22/0x30 > > > > > [ 871.346239] > > > > > [ 871.347060] Modules linked in: snd_hda_codec_generic ledtrig_a= udio snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec snd_hd= a_core snd_hwdep snd_seq snd_seq_device joydev snd_pcm intel_rapl_msr ppdev= intel_rapl_common snd_timer pcspkr e1000e snd soundcore i2c_piix4 parport_= pc parport loop fuse xenfs dm_crypt crct10dif_pclmul crc32_pclmul crc32c_in= tel polyval_clmulni polyval_generic floppy ghash_clmulni_intel sha512_ssse3= serio_raw virtio_scsi virtio_console bochs xhci_pci xhci_pci_renesas xhci_= hcd qemu_fw_cfg drm_vram_helper drm_ttm_helper ttm ata_generic pata_acpi xe= n_privcmd xen_pciback xen_blkback xen_gntalloc xen_gntdev xen_evtchn scsi_d= h_rdac scsi_dh_emc scsi_dh_alua uinput dm_multipath > > > > > [ 871.368892] CR2: 0000000000000000 > > > > > [ 871.370160] ---[ end trace 0000000000000000 ]--- > > > > > [ 871.371719] RIP: e030:__wake_up_common+0x4c/0x180 > > > > > [ 871.373273] Code: 24 0c 89 4c 24 08 4d 85 c9 74 0a 41 f6 01 04= 0f 85 a3 00 00 00 48 8b 43 08 4c 8d 40 e8 48 83 c3 08 49 8d 40 18 48 39 c3= 74 5b <49> 8b 40 18 31 ed 4c 8d 70 e8 45 8b 28 41 f6 c5 04 75 5f 49 8b 40 > > > > > [ 871.379866] RSP: e02b:ffffc900400f7e10 EFLAGS: 00010082 > > > > > [ 871.381689] RAX: 0000000000000000 RBX: ffff88810541ce98 RCX: 0= 000000000000000 > > > > > [ 871.383971] RDX: 0000000000000001 RSI: 0000000000000003 RDI: f= fff88810541ce90 > > > > > [ 871.386235] RBP: ffffc900400f0280 R08: ffffffffffffffe8 R09: f= fffc900400f7e68 > > > > > [ 871.388521] R10: 0000000000007ff0 R11: ffff888100ad3000 R12: f= fffc900400f7e68 > > > > > [ 871.390789] R13: 0000000000000000 R14: 0000000000000000 R15: 0= 000000000000000 > > > > > [ 871.393101] FS: 0000000000000000(0000) GS:ffff88813ff00000(00= 00) knlGS:0000000000000000 > > > > > [ 871.395671] CS: 10000e030 DS: 0000 ES: 0000 CR0: 000000008005= 0033 > > > > > [ 871.397863] CR2: 0000000000000000 CR3: 00000001067fe000 CR4: 0= 000000000040660 > > > > > [ 871.400441] Kernel panic - not syncing: Fatal exception > > > > > [ 871.402171] Kernel Offset: disabled > > > > > (XEN) Hardware Dom0 crashed: rebooting machine in 5 seconds. > > > > >=20 > > > > > It isn't the first time I see similar crash, but I can't really > > > > > reproduce it reliably. Restarted test usually passes. > > > > > Note this is Xen nested in KVM, so it could very well be some odd= ity > > > > > about nested virt, although looking at the stack trace, it's unli= kely > > > > > and more likely some race condition hit only on slower system. > > > >=20 > > > > Recently I've got the same crash on a real system in domU too. And = also > > > > on nested on newer kernel 6.1.57 (here it happened in dom0). So, th= is is > > > > still an issue and affects not only nested case :/ > > > >=20 > > > > > Unfortunately I don't have symbols for this kernel handy, but the= re is a > > > > > single wake_up() call in process_writes(), so it shouldn't be an = issue. > > > > >=20 > > > > > Any ideas? > > > > >=20 > > > > > Full log at https://openqa.qubes-os.org/tests/80779/logfile?filen= ame=3Dserial0.txt > > > >=20 > > > > More links at https://github.com/QubesOS/qubes-issues/issues/8638, > > > > including more recent stack trace. > > >=20 > > > Happens on 6.1.75 too (new stack trace I've added to the issue above, > > > but it's pretty similar). >=20 > Recently I've got a report from another user about similar issue, on > 6.6.29 this time. I also still encounter this issue once a month or so, > but the user claims they get it much more often: > https://github.com/QubesOS/qubes-issues/issues/8638#issuecomment-21354198= 96 > The extra conditions reported by the user are: > - old AMD system (KGPE-D16 with Opteron 6282 SE) requiring > `spec-ctrl=3Dibpb-entry=3Dno-pv` to remain usable=20 > - Whonix domU, which has a bunch of sysctl parameters changed, listed > at: > - https://github.com/Kicksecure/security-misc > - https://github.com/Kicksecure/security-misc/blob/master/usr/lib/sysct= l.d/990-security-misc.conf > (unsure which are relevant, maybe `vm.swappiness=3D1`?) I've got some more report confirming it's still happening on Linux 6.12.18. Is there anything I can do to help fixing this? Maybe ask users to enable some extra logging? --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab --uA3h3C1LK1Wh2sS5 Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmgI4BgACgkQ24/THMrX 1yyQBAf8D7f65wbZUtO4YalAr6PhZYm1DhkE0BxUVDqawo/RChapo9A7WhAxomiS POyiqlbW5nnQVOykwoV7cAiu5LBnspC2UPtzyy76VxBoyGRWXKr+S8lEVbx9uFki uQOe9oRom7VIsoUg5BRYswbNb+1urUyp3UU9hikczp/GDbDbgzGvbEkxSIy/19lx a4xgTYZ6sXXuAcC4QxUemuglPYeP1mwsTWYS9cDW0PMB83+hLTNw+aE3/o14mPTL mxEw0gN/sjLH0blxZjowyLSWV2Xmp3I9FMGt+f3yOn+VQ4zOHHyxK+2oqqO4ZN5k iuvxlktyTmUtc2jBQvRHMnJgJIUbOQ== =b/on -----END PGP SIGNATURE----- --uA3h3C1LK1Wh2sS5--