[Bug 2162843] Lspci.txt

apport information ** Attachment added: "Lspci.txt" https://bugs.launchpad.net/bugs/2162843/+attachment/5989460/+files/Lspci.txt -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2162843 Title: Regression: io_uring provided buffer ring registration (IORING_REGISTER_PBUF_RING) returns -EINVAL for valid requests on 6.8.0-136 and 6.8.0-137 Status in linux package in Ubuntu: New Bug description: SUMMARY Starting with linux-image-6.8.0-136-generic (noble/24.04), registering an io_uring provided buffer ring (IORING_REGISTER_PBUF_RING) with a valid struct io_uring_buf_reg fails with EINVAL (errno 22). It succeeds on 6.8.0-134-generic and on mainline 7.0.0-28-generic. 6.8.0-137-generic is also affected, so the defect is carried in the noble 6.8 branch, not a one-off build. Provided buffer rings are a standard, documented io_uring feature, so this breaks any application that uses them. REPRODUCED ON OUR HARDWARE (single machine, kernel is the only variable) Same host, booted each kernel in turn and ran the attached reproducer: 6.8.0-134-generic -> register_buf_ring: OK 6.8.0-136-generic -> register_buf_ring: Invalid argument (EINVAL) 6.8.0-134-generic -> OK again after rebooting back A production networking service on that host that registers an io_uring buffer ring on startup aborts under -136 with SIGABRT (systemd Result: core-dump) at the failed registration, and starts normally again on -134. uname -a on the failing boot: Linux 6.8.0-136-generic #136-Ubuntu SMP PREEMPT_DYNAMIC Wed Jul 1 21:53:05 UTC 2026 x86_64 STEPS TO REPRODUCE Build and run the attached pbufring.c (pure liburing, ~20 lines): sudo apt-get install -y liburing-dev gcc gcc -o pbufring pbufring.c -luring ./pbufring Expected (good kernel): register_buf_ring: OK Observed (6.8.0-136 / -137): register_buf_ring: Invalid argument kernel.io_uring_disabled = 0 and /proc/sys/kernel/io_uring_group = -1 on all machines, so this is not an io_uring lockdown / AppArmor difference; the registration path itself rejects a valid request. SUSPECTED CAUSE Failure is in io_uring provided-buffer-ring registration validation (io_uring/kbuf.c, io_register_pbuf_ring(), reserved-field / struct checking). A valid io_uring_buf_reg (reserved fields zeroed; ring_addr/ring_entries/bgid set) is rejected; mainline is fine. Please check the noble backport of that validation, in particular the cherry-pick of upstream commit 1724849072854a66861d461b298b04612702d685 ("io_uring/kbuf: use mem_is_zero()"), which replaced the manual reg.resv[0]||resv[1]||resv[2] check with a mem_is_zero() call. If applied over the wrong offset/size it would zero-check bytes that legitimately carry ring_addr/ring_entries/bgid and reject every real registration. Note the current noble git tip shows the correct manual resv check, so a fix may already be staged; please confirm whether it is queued for 6.8.0-138 and expedite, since -137 shipped still broken. WORKAROUNDS (not fixes) Downgrade to 6.8.0-134-generic and reboot; or, application-side, avoid the provided- buffer-ring path where the code supports a fallback. ENVIRONMENT Ubuntu 24.04 LTS (noble), x86_64. Regression introduced between 6.8.0-134 and 6.8.0-136; also present in 6.8.0-137. --- ProblemType: Bug AlsaDevices: total 0 crw-rw---- 1 root audio 116, 1 Aug 4 10:34 seq crw-rw---- 1 root audio 116, 33 Aug 4 10:34 timer AlsaVersion: Advanced Linux Sound Architecture Driver Version k6.8.0-134-generic. AplayDevices: Error: [Errno 2] No such file or directory: 'aplay' ApportVersion: 2.28.1-0ubuntu3.8 Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord' AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1: CRDA: N/A CasperMD5CheckResult: unknown CloudArchitecture: x86_64 CloudBuildName: server CloudID: configdrive CloudName: configdrive CloudPlatform: configdrive CloudSerial: 20250122 CloudSubPlatform: config-disk (/dev/nvme0n1p5) DistroRelease: Ubuntu 24.04 IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig' MachineType: AsrockRack To be filled by O.E.M. NonfreeKernelModules: zfs Package: linux (not installed) ProcEnviron: LANG=C.UTF-8 PATH=(custom, no user) SHELL=/bin/bash TERM=xterm-256color ProcFB: 0 simpledrmdrmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-6.8.0-134-generic root=UUID=c0b38019-7891-470a-b184-151bcdd42d58 ro nomodeset iommu=pt console=tty0 console=ttyS1,115200n8 amd_pstate=disable quiet splash ipv6.disable=1 vt.handoff=7 ProcVersionSignature: Ubuntu 6.8.0-134.134-generic 6.8.12 RelatedPackageVersions: linux-restricted-modules-6.8.0-134-generic N/A linux-backports-modules-6.8.0-134-generic N/A linux-firmware 20240318.git3b128b60-0ubuntu2.27 RfKill: Error: [Errno 2] No such file or directory: 'rfkill' Tags: cloud-image noble Uname: Linux 6.8.0-134-generic x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: N/A _MarkForUpload: True dmi.bios.date: 10/17/2024 dmi.bios.release: 5.35 dmi.bios.vendor: American Megatrends International, LLC. dmi.bios.version: 20.01.OV03 dmi.board.asset.tag: To be filled by O.E.M. dmi.board.name: B650D4U3-2Q/BCM dmi.board.vendor: ASRockRack dmi.board.version: 3.01A dmi.chassis.asset.tag: To be filled by O.E.M. dmi.chassis.type: 17 dmi.chassis.vendor: To be filled by O.E.M. dmi.chassis.version: To be filled by O.E.M. dmi.modalias: dmi:bvnAmericanMegatrendsInternational,LLC.:bvr20.01.OV03:bd10/17/2024:br5.35:svnAsrockRack:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnASRockRack:rnB650D4U3-2Q/BCM:rvr3.01A:cvnTobefilledbyO.E.M.:ct17:cvrTobefilledbyO.E.M.:skuTobefilledbyO.E.M.: dmi.product.family: To be filled by O.E.M. dmi.product.name: To be filled by O.E.M. dmi.product.sku: To be filled by O.E.M. dmi.product.version: To be filled by O.E.M. dmi.sys.vendor: AsrockRack To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2162843/+subscriptions