XPost: linux.debian.bugs.dist, linux.kernel   
   From: carnil@debian.org   
      
   Hi,   
      
   On Fri, Nov 14, 2025 at 08:05:55PM +0530, Naman Jain wrote:   
   >    
   >    
   > On 11/14/2025 5:19 PM, Peter Morrow wrote:   
   > > Hi Naman,   
   > >    
   > > On Fri, 14 Nov 2025 at 06:03, Naman Jain    
   wrote:   
   > > >    
   > > >    
   > > >    
   > > > On 11/13/2025 11:59 PM, Salvatore Bonaccorso wrote:   
   > > > > 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,   
   > > > > >    
   > > > > > 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 details   
   > > > > > of the system using a previously known good version. The panic is   
   happening   
   > > > > > 100% of the time unfortunately. I have access to the serial console   
   however   
   > > > > > so can enable any required verbose logging during boot if necessary.   
   > > > > >    
   > > > > > Crucially the crash is not seen with kernel version 6.   
   2.41+deb13-amd64 with the   
   > > > > > same userspace. We had pinned to that version until very recently to   
   in order   
   > > > > > to work around https://bugs.debian.org/cgi-bin/bugrepo   
   t.cgi?bug=1109676   
   > > > > >    
   > > > > > I'm running a dpdk application here (VPP) on Azure, VM form factor   
   is a   
   > > > > > "Standard DS3 v2 (4 vcpus, 14 GiB memory)".   
   > > > > >    
   > > > > > The only relevant upstream commit in this area (as far as I can see)   
   is:   
   > > > > >    
   > > > > > https://lore.kernel.org/linux-hyperv/1bb599ee-fe28-409   
   -b430-2fc086268936@linux.microsoft.com/   
   > > > > >    
   > > > > > The comment regarding avoiding races at start adds a bit more weight   
   behind this   
   > > > > > hunch, though it's only a hunch as I am most definitely nowhere near   
   an expert   
   > > > > > in this area.   
   > > > > >    
   > > > > > -- Package-specific info:   
   > > > > >    
   > > > > > [   19.625535] BUG: kernel NULL pointer dereference, address:   
   00000000000000a0   
   > > > > > [   19.628874] #PF: supervisor read access in kernel mode   
   > > > > > [   19.630841] #PF: error_code(0x0000) - not-present page   
   > > > > > [   19.632788] PGD 0 P4D 0   
   > > > > > [   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+deb13-amd64 #1  Debian 6.12.57-1   
   > > > > > [   19.640216] Hardware name: Microsoft Corporation Virtual   
   Machine/Virtual 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 90 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:   
   0000000000000015   
   > > > > > [   19.659240] RDX: 0000000000000001 RSI: ffffffffffffffff RDI:   
   ffff8ff69c759400   
   > > > > > [   19.662168] RBP: ffff8ff548790200 R08: ffff8ff548790200 R09:   
   00fca75150b080e9   
   > > > > > [   19.665239] R10: 0000000000000000 R11: ffffb15ac01a4ff8 R12:   
   ffff8ff871dc1480   
   > > > > > [   19.668193] R13: ffff8ff69c759400 R14: ffff8ff69c7596a0 R15:   
   ffffffffc106e160   
   > > > > > [   19.671106] FS:  0000000000000000(0000) GS:ffff8ff871d80000(0000)   
   knlGS:0000000000000000   
   > > > > > [   19.674281] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033   
   > > > > > [   19.676533] CR2: 00000000000000a0 CR3: 0000000100ba6003 CR4:   
   00000000003706f0   
   > > > > > [   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 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d e5 3b 31 00 fb f4   
    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:   
   ffff8ff54c64ce30   
   > > > > > [   19.704328] RDX: 0000000000000000 RSI: 0000000000000003 RDI:   
   000000000001f894   
   > > > > > [   19.706910] RBP: 0000000000000003 R08: 000000000bb760d9 R09:   
   00fca75150b080e9   
   > > > > > [   19.709762] R10: 0000000000000003 R11: 0000000000000001 R12:   
   0000000000000000   
   > > > > > [   19.712510] R13: 0000000000000000 R14: 0000000000000000 R15:   
   0000000000000000   
   > > > > > [   19.715173]  default_idle+0x9/0x20   
      
   [continued in next message]   
      
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