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[82.192.244.13]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4778c88c068sm47292975e9.9.2025.11.13.10.29.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Nov 2025 10:29:40 -0800 (PST) Sender: Salvatore Bonaccorso Received: by eldamar.lan (Postfix, from userid 1000) id 93E03BE2EE7; Thu, 13 Nov 2025 19:29:39 +0100 (CET) Date: Thu, 13 Nov 2025 19:29:39 +0100 From: Salvatore Bonaccorso To: Naman Jain , John Starks , Michael Kelley , Long Li , Tianyu Lan , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Greg Kroah-Hartman , Peter Morrow Cc: 1120602@bugs.debian.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, regressions@lists.linux.dev, stable@vger.kernel.org Subject: [REGRESSION 6.12.y] hyper-v: BUG: kernel NULL pointer dereference, address: 00000000000000a0: RIP: 0010:hv_uio_channel_cb+0xd/0x20 [uio_hv_generic] Message-ID: Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Peter Morrow reported in Debian a regression, reported in https://bugs.debian.org/1120602 . The regression was seen after updating, to 6.12.57-1 in Debian, but details on the offending commit follows. His report was as follows: > Dear Maintainer, >=20 > I'm seeing a kernel crash quite soon after boot on a debian trixie based > system running 6.12.57+deb13-amd64, unfortunately the kernel panics before > I can access the system to gather more information. Thus I'll provide det= ails > of the system using a previously known good version. The panic is happeni= ng > 100% of the time unfortunately. I have access to the serial console howev= er > so can enable any required verbose logging during boot if necessary. >=20 > Crucially the crash is not seen with kernel version 6.12.41+deb13-amd64 w= ith the > same userspace. We had pinned to that version until very recently to in o= rder > to work around https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=3D1109676 >=20 > I'm running a dpdk application here (VPP) on Azure, VM form factor is a > "Standard DS3 v2 (4 vcpus, 14 GiB memory)". >=20 > The only relevant upstream commit in this area (as far as I can see) is: >=20 > https://lore.kernel.org/linux-hyperv/1bb599ee-fe28-409d-b430-2fc086268936= @linux.microsoft.com/ >=20 > The comment regarding avoiding races at start adds a bit more weight behi= nd this > hunch, though it's only a hunch as I am most definitely nowhere near an e= xpert > in this area. >=20 > -- Package-specific info: >=20 > [ 19.625535] BUG: kernel NULL pointer dereference, address: 00000000000= 000a0 > [ 19.628874] #PF: supervisor read access in kernel mode > [ 19.630841] #PF: error_code(0x0000) - not-present page > [ 19.632788] PGD 0 P4D 0=20 > [ 19.633905] Oops: Oops: 0000 [#1] PREEMPT SMP PTI > [ 19.635586] CPU: 3 UID: 0 PID: 0 Comm: swapper/3 Not tainted 6.12.57+d= eb13-amd64 #1 Debian 6.12.57-1 > [ 19.640216] Hardware name: Microsoft Corporation Virtual Machine/Virtu= al Machine, BIOS Hyper-V UEFI Release v4.1 09/28/2024 > [ 19.644514] RIP: 0010:hv_uio_channel_cb+0xd/0x20 [uio_hv_generic] > [ 19.646994] Code: 02 00 00 5b 5d e9 53 98 69 e9 0f 1f 00 90 90 90 90 9= 0 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 47 10 <= 48> 8b b8 a0 00 00 00 f0 83 44 24 fc 00 e9 51 6f fa ff 90 90 90 90 > [ 19.654377] RSP: 0018:ffffb15ac01a4fa8 EFLAGS: 00010046 > [ 19.656385] RAX: 0000000000000000 RBX: 0000000000000015 RCX: 000000000= 0000015 > [ 19.659240] RDX: 0000000000000001 RSI: ffffffffffffffff RDI: ffff8ff69= c759400 > [ 19.662168] RBP: ffff8ff548790200 R08: ffff8ff548790200 R09: 00fca7515= 0b080e9 > [ 19.665239] R10: 0000000000000000 R11: ffffb15ac01a4ff8 R12: ffff8ff87= 1dc1480 > [ 19.668193] R13: ffff8ff69c759400 R14: ffff8ff69c7596a0 R15: ffffffffc= 106e160 > [ 19.671106] FS: 0000000000000000(0000) GS:ffff8ff871d80000(0000) knlG= S:0000000000000000 > [ 19.674281] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 19.676533] CR2: 00000000000000a0 CR3: 0000000100ba6003 CR4: 000000000= 03706f0 > [ 19.679385] Call Trace: > [ 19.680361] > [ 19.681181] vmbus_isr+0x1a5/0x210 [hv_vmbus] > [ 19.682916] __sysvec_hyperv_callback+0x32/0x60 > [ 19.684991] sysvec_hyperv_callback+0x6c/0x90 > [ 19.686665] > [ 19.687509] > [ 19.688366] asm_sysvec_hyperv_callback+0x1a/0x20 > [ 19.690262] RIP: 0010:pv_native_safe_halt+0xf/0x20 > [ 19.692067] Code: 09 e9 c5 08 01 00 0f 1f 44 00 00 90 90 90 90 90 90 9= 0 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d e5 3b 31 00 fb f4 <= c3> cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 > [ 19.699119] RSP: 0018:ffffb15ac0103ed8 EFLAGS: 00000246 > [ 19.701412] RAX: 0000000000000003 RBX: ffff8ff5403b1fc0 RCX: ffff8ff54= c64ce30 > [ 19.704328] RDX: 0000000000000000 RSI: 0000000000000003 RDI: 000000000= 001f894 > [ 19.706910] RBP: 0000000000000003 R08: 000000000bb760d9 R09: 00fca7515= 0b080e9 > [ 19.709762] R10: 0000000000000003 R11: 0000000000000001 R12: 000000000= 0000000 > [ 19.712510] R13: 0000000000000000 R14: 0000000000000000 R15: 000000000= 0000000 > [ 19.715173] default_idle+0x9/0x20 > [ 19.716846] default_idle_call+0x29/0x100 > [ 19.718623] do_idle+0x1fe/0x240 > [ 19.720045] cpu_startup_entry+0x29/0x30 > [ 19.721595] start_secondary+0x11e/0x140 > [ 19.723080] common_startup_64+0x13e/0x141 > [ 19.725222] > [ 19.726387] Modules linked in: isofs cdrom uio_hv_generic uio binfmt_m= isc intel_rapl_msr intel_rapl_common intel_uncore_frequency_common isst_if_= mbox_msr isst_if_common rpcrdma skx_edac_common nfit sunrpc libnvdimm crct1= 0dif_pclmul ghash_clmulni_intel sha512_ssse3 sha256_ssse3 rdma_ucm ib_iser = sha1_ssse3 rdma_cm aesni_intel iw_cm gf128mul crypto_simd libiscsi cryptd i= b_umad ib_ipoib scsi_transport_iscsi ib_cm rapl sg hv_utils hv_balloon evde= v pcspkr joydev mpls_router ip_tunnel ramoops configfs pstore_blk efi_pstor= e pstore_zone nfnetlink vsock_loopback vmw_vsock_virtio_transport_common hv= _sock vmw_vsock_vmci_transport vsock vmw_vmci efivarfs ip_tables x_tables a= utofs4 overlay squashfs dm_verity dm_bufio reed_solomon dm_mod loop ext4 cr= c16 mbcache jbd2 crc32c_generic mlx5_ib ib_uverbs ib_core mlx5_core mlxfw p= ci_hyperv pci_hyperv_intf hyperv_drm drm_shmem_helper sd_mod drm_kms_helper= hv_storvsc scsi_transport_fc drm scsi_mod hid_generic hid_hyperv hid serio= _raw hv_netvsc hyperv_keyboard scsi_common hv_vmbus > [ 19.726466] crc32_pclmul crc32c_intel > [ 19.765771] CR2: 00000000000000a0 > [ 19.767524] ---[ end trace 0000000000000000 ]--- > [ 19.800433] RIP: 0010:hv_uio_channel_cb+0xd/0x20 [uio_hv_generic] > [ 19.803170] Code: 02 00 00 5b 5d e9 53 98 69 e9 0f 1f 00 90 90 90 90 9= 0 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 47 10 <= 48> 8b b8 a0 00 00 00 f0 83 44 24 fc 00 e9 51 6f fa ff 90 90 90 90 > [ 19.811041] RSP: 0018:ffffb15ac01a4fa8 EFLAGS: 00010046 > [ 19.813466] RAX: 0000000000000000 RBX: 0000000000000015 RCX: 000000000= 0000015 > [ 19.816504] RDX: 0000000000000001 RSI: ffffffffffffffff RDI: ffff8ff69= c759400 > [ 19.819484] RBP: ffff8ff548790200 R08: ffff8ff548790200 R09: 00fca7515= 0b080e9 > [ 19.822625] R10: 0000000000000000 R11: ffffb15ac01a4ff8 R12: ffff8ff87= 1dc1480 > [ 19.825569] R13: ffff8ff69c759400 R14: ffff8ff69c7596a0 R15: ffffffffc= 106e160 > [ 19.828804] FS: 0000000000000000(0000) GS:ffff8ff871d80000(0000) knlG= S:0000000000000000 > [ 19.832214] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 19.834709] CR2: 00000000000000a0 CR3: 0000000100ba6003 CR4: 000000000= 03706f0 > [ 19.837976] Kernel panic - not syncing: Fatal exception in interrupt > [ 19.841825] Kernel Offset: 0x28a00000 from 0xffffffff81000000 (relocat= ion range: 0xffffffff80000000-0xffffffffbfffffff) > [ 19.896620] ---[ end Kernel panic - not syncing: Fatal exception in in= terrupt ]--- >=20 >=20 > lspci output: >=20 > Collected from a system that is not crashing (6.12.41+deb13-amd64 #1 SMP = PREEMPT_DYNAMIC Debian 6.12.41-1 (2025-08-12) x86_64 GNU/Linux)... >=20 > $ sudo lspci -v > 2f22:00:02.0 Ethernet controller: Mellanox Technologies MT27710 Family [C= onnectX-4 Lx Virtual Function] (rev 80) > Subsystem: Mellanox Technologies Device 0190 > Physical Slot: 3 > Flags: bus master, fast devsel, latency 0, NUMA node 0 > Memory at fe0100000 (64-bit, prefetchable) [size=3D1M] > Capabilities: [60] Express Endpoint, IntMsgNum 0 > Capabilities: [9c] MSI-X: Enable+ Count=3D8 Masked- > Kernel driver in use: mlx5_core > Kernel modules: mlx5_core >=20 > 52f7:00:02.0 Ethernet controller: Mellanox Technologies MT27710 Family [C= onnectX-4 Lx Virtual Function] (rev 80) > Subsystem: Mellanox Technologies Device 0190 > Physical Slot: 2 > Flags: bus master, fast devsel, latency 0, NUMA node 0 > Memory at fe0000000 (64-bit, prefetchable) [size=3D1M] > Capabilities: [60] Express Endpoint, IntMsgNum 0 > Capabilities: [9c] MSI-X: Enable+ Count=3D8 Masked- > Kernel driver in use: mlx5_core > Kernel modules: mlx5_core >=20 > 7852:00:02.0 Ethernet controller: Mellanox Technologies MT27710 Family [C= onnectX-4 Lx Virtual Function] (rev 80) > Subsystem: Mellanox Technologies Device 0190 > Physical Slot: 4 > Flags: bus master, fast devsel, latency 0, NUMA node 0 > Memory at fe0200000 (64-bit, prefetchable) [size=3D1M] > Capabilities: [60] Express Endpoint, IntMsgNum 0 > Capabilities: [9c] MSI-X: Enable+ Count=3D8 Masked- > Kernel driver in use: mlx5_core > Kernel modules: mlx5_core >=20 > dmidecode output: >=20 > $ sudo dmidecode=20 > # dmidecode 3.6 > Getting SMBIOS data from sysfs. > SMBIOS 3.1.0 present. > Table at 0x3FF82000. >=20 > Handle 0x0000, DMI type 0, 26 bytes > BIOS Information > Vendor: Microsoft Corporation > Version: Hyper-V UEFI Release v4.1 > Release Date: 05/13/2024 > ROM Size: 64 kB > Characteristics: > BIOS characteristics not supported > ACPI is supported > Targeted content distribution is supported > UEFI is supported > System is a virtual machine > BIOS Revision: 4.1 >=20 > Handle 0x0001, DMI type 1, 27 bytes > System Information > Manufacturer: Microsoft Corporation > Product Name: Virtual Machine > Version: Hyper-V UEFI Release v4.1 > Serial Number: 0000-0010-5437-9499-5225-4477-46 > UUID: 925315af-4af4-4d42-915a-1516b5a1fe5c > Wake-up Type: Power Switch > SKU Number: None > Family: Virtual Machine >=20 > Handle 0x0002, DMI type 3, 24 bytes > Chassis Information > Manufacturer: Microsoft Corporation > Type: Desktop > Lock: Not Present > Version: Hyper-V UEFI Release v4.1 > Serial Number: 2466-9316-1078-9783-6078-7718-80 > Asset Tag: 7783-7084-3265-9085-8269-3286-77 > Boot-up State: Safe > Power Supply State: Safe > Thermal State: Safe > Security Status: Unknown > OEM Information: 0x00000000 > Height: Unspecified > Number Of Power Cords: Unspecified > Contained Elements: 0 > SKU Number: Virtual Machine >=20 > Handle 0x0003, DMI type 2, 17 bytes > Base Board Information > Manufacturer: Microsoft Corporation > Product Name: Virtual Machine > Version: Hyper-V UEFI Release v4.1 > Serial Number: 0000-0010-4737-0707-0684-2660-76 > Asset Tag: None > Features: > Board is a hosting board > Location In Chassis: Virtual Machine > Chassis Handle: 0x0002 > Type: Motherboard > Contained Object Handles: 0 >=20 > Handle 0x0004, DMI type 4, 48 bytes > Processor Information > Socket Designation: None > Type: Central Processor > Family: Unknown > Manufacturer: None > ID: 00 00 00 00 00 00 00 00 > Version: None > Voltage: Unknown > External Clock: Unknown > Max Speed: Unknown > Current Speed: Unknown > Status: Unpopulated > Upgrade: Other > L1 Cache Handle: Not Provided > L2 Cache Handle: Not Provided > L3 Cache Handle: Not Provided > Serial Number: None > Asset Tag: None > Part Number: None > Core Count: 4 > Core Enabled: 4 > Thread Count: 1 > Characteristics: None >=20 > Handle 0x0005, DMI type 11, 5 bytes > OEM Strings > String 1: [MS_VM_CERT/SHA1/9b80ca0d5dd061ec9da4e494f4c3fd1196270c= 22] > String 2: None > String 3: To be filled by OEM >=20 > Handle 0x0006, DMI type 16, 23 bytes > Physical Memory Array > Location: System Board Or Motherboard > Use: System Memory > Error Correction Type: None > Maximum Capacity: 0 bytes > Error Information Handle: Not Provided > Number Of Devices: 3 >=20 > Handle 0x0007, DMI type 17, 92 bytes > Memory Device > Array Handle: 0x0006 > Error Information Handle: Not Provided > Total Width: Unknown > Data Width: Unknown > Size: 26 MB > Form Factor: Unknown > Set: None > Locator: M0001 > Bank Locator: None > Type: Unknown > Type Detail: Unknown > Speed: Unknown > Manufacturer: Microsoft Corporation > Serial Number: None > Asset Tag: None > Part Number: None > Rank: Unknown > Configured Memory Speed: Unknown > Minimum Voltage: Unknown > Maximum Voltage: Unknown > Configured Voltage: Unknown > Memory Technology: > Memory Operating Mode Capability: None > Firmware Version: Not Specified > Module Manufacturer ID: Unknown > Module Product ID: Unknown > Memory Subsystem Controller Manufacturer ID: Unknown > Memory Subsystem Controller Product ID: Unknown > Non-Volatile Size: None > Volatile Size: None > Cache Size: None > Logical Size: None >=20 > Handle 0x0008, DMI type 19, 31 bytes > Memory Array Mapped Address > Starting Address: 0x00000000000 > Ending Address: 0x00001A003FF > Range Size: 26625 kB > Physical Array Handle: 0x0006 > Partition Width: 0 >=20 > Handle 0x0009, DMI type 20, 35 bytes > Memory Device Mapped Address > Starting Address: 0x00000000000 > Ending Address: 0x00001A003FF > Range Size: 26625 kB > Physical Device Handle: 0x0007 > Memory Array Mapped Address Handle: 0x0008 > Partition Row Position: Unknown >=20 > Handle 0x000A, DMI type 17, 92 bytes > Memory Device > Array Handle: 0x0006 > Error Information Handle: Not Provided > Total Width: Unknown > Data Width: Unknown > Size: 948 MB > Form Factor: Unknown > Set: None > Locator: M0002 > Bank Locator: None > Type: Unknown > Type Detail: Unknown > Speed: Unknown > Manufacturer: Microsoft Corporation > Serial Number: None > Asset Tag: None > Part Number: None > Rank: Unknown > Configured Memory Speed: Unknown > Minimum Voltage: Unknown > Maximum Voltage: Unknown > Configured Voltage: Unknown > Memory Technology: > Memory Operating Mode Capability: None > Firmware Version: Not Specified > Module Manufacturer ID: Unknown > Module Product ID: Unknown > Memory Subsystem Controller Manufacturer ID: Unknown > Memory Subsystem Controller Product ID: Unknown > Non-Volatile Size: None > Volatile Size: None > Cache Size: None > Logical Size: None >=20 > Handle 0x000B, DMI type 19, 31 bytes > Memory Array Mapped Address > Starting Address: 0x00004C00000 > Ending Address: 0x000400003FF > Range Size: 970753 kB > Physical Array Handle: 0x0006 > Partition Width: 0 >=20 > Handle 0x000C, DMI type 20, 35 bytes > Memory Device Mapped Address > Starting Address: 0x00004C00000 > Ending Address: 0x000400003FF > Range Size: 970753 kB > Physical Device Handle: 0x000A > Memory Array Mapped Address Handle: 0x000B > Partition Row Position: Unknown >=20 > Handle 0x000D, DMI type 17, 92 bytes > Memory Device > Array Handle: 0x0006 > Error Information Handle: Not Provided > Total Width: Unknown > Data Width: Unknown > Size: 13 GB > Form Factor: Unknown > Set: None > Locator: M0003 > Bank Locator: None > Type: Unknown > Type Detail: Unknown > Speed: Unknown > Manufacturer: Microsoft Corporation > Serial Number: None > Asset Tag: None > Part Number: None > Rank: Unknown > Configured Memory Speed: Unknown > Minimum Voltage: Unknown > Maximum Voltage: Unknown > Configured Voltage: Unknown > Memory Technology: > Memory Operating Mode Capability: None > Firmware Version: Not Specified > Module Manufacturer ID: Unknown > Module Product ID: Unknown > Memory Subsystem Controller Manufacturer ID: Unknown > Memory Subsystem Controller Product ID: Unknown > Non-Volatile Size: None > Volatile Size: None > Cache Size: None > Logical Size: None >=20 > Handle 0x000E, DMI type 19, 31 bytes > Memory Array Mapped Address > Starting Address: 0x00100000000 > Ending Address: 0x004400003FF > Range Size: 13 GB > Physical Array Handle: 0x0006 > Partition Width: 0 >=20 > Handle 0x000F, DMI type 20, 35 bytes > Memory Device Mapped Address > Starting Address: 0x00100000000 > Ending Address: 0x004400003FF > Range Size: 13 GB > Physical Device Handle: 0x000D > Memory Array Mapped Address Handle: 0x000E > Partition Row Position: Unknown >=20 > Handle 0x0010, DMI type 32, 11 bytes > System Boot Information > Status: No errors detected >=20 > Handle 0xFEFF, DMI type 127, 4 bytes > End Of Table The offending commit appers to be the backport of b15b7d2a1b09 ("uio_hv_generic: Let userspace take care of interrupt mask") for 6.12.y. Peter confirmed that reverting this commit on top of 6.12.57-1 as packaged in Debian resolves indeed the issue. Interestingly the issue is *not* seen with 6.17.7 based kernel in Debian. #regzbot introduced: 37bd91f22794dc05436130d6983302cb90ecfe7e #regzbot monitor: https://bugs.debian.org/1120602 Thank you already! Regards, Salvatore