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Cancelling the I/O and admin tagsets during nvme-loop controller reset or shutdown is unnecessary. The subsequent destruction of the I/O and admin queues already waits for all in-flight target operations to complete. Cancelling the tagsets first also opens a race window. After a request tag has been cancelled, a late completion from the target may still arrive before the queues are destroyed. In that case the completion path may access a request whose tag has already been cancelled or freed, which can lead to a kernel crash. Please see below the kernel crash encountered while running blktests nvme/040: run blktests nvme/040 at 2026-03-08 06:34:27 loop0: detected capacity change from 0 to 2097152 nvmet: adding nsid 1 to subsystem blktests-subsystem-1 nvmet: Created nvm controller 1 for subsystem blktests-subsystem-1 for NQN nqn.2014-08.org.nvmexpress:uuid:0f01fb42-9f7f-4856-b0b3-51e60b8de349. nvme nvme6: creating 96 I/O queues. nvme nvme6: new ctrl: "blktests-subsystem-1" nvme_log_error: 1 callbacks suppressed block nvme6n1: no usable path - requeuing I/O nvme6c6n1: Read(0x2) @ LBA 2096384, 128 blocks, Host Aborted Command (sct 0x3 / sc 0x71) blk_print_req_error: 1 callbacks suppressed I/O error, dev nvme6c6n1, sector 2096384 op 0x0:(READ) flags 0x2880700 phys_seg 1 prio class 2 block nvme6n1: no usable path - requeuing I/O Kernel attempted to read user page (236) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x00000236 Faulting instruction address: 0xc000000000961274 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries Modules linked in: nvme_loop nvme_fabrics loop nvmet null_blk rpadlpar_io rpaphp xsk_diag bonding rfkill nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink pseries_rng dax_pmem vmx_crypto drm drm_panel_orientation_quirks xfs mlx5_core nvme bnx2x sd_mod nd_pmem nd_btt nvme_core sg papr_scm tls libnvdimm ibmvscsi ibmveth scsi_transport_srp nvme_keyring nvme_auth mdio hkdf pseries_wdt dm_mirror dm_region_hash dm_log dm_mod fuse [last unloaded: loop] CPU: 25 UID: 0 PID: 0 Comm: swapper/25 Kdump: loaded Not tainted 7.0.0-rc3+ #14 PREEMPT Hardware name: IBM,9043-MRX Power11 (architected) 0x820200 0xf000007 of:IBM,FW1120.00 (RF1120_128) hv:phyp pSeries NIP: c000000000961274 LR: c008000009af1808 CTR: c00000000096124c REGS: c0000007ffc0f910 TRAP: 0300 Not tainted (7.0.0-rc3+) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 22222222 XER: 00000000 CFAR: c008000009af232c DAR: 0000000000000236 DSISR: 40000000 IRQMASK: 0 GPR00: c008000009af17fc c0000007ffc0fbb0 c000000001c78100 c0000000be05cc00 GPR04: 0000000000000001 0000000000000000 0000000000000007 0000000000000000 GPR08: 0000000000000000 0000000000000000 0000000000000002 c008000009af2318 GPR12: c00000000096124c c0000007ffdab880 0000000000000000 0000000000000000 GPR16: 0000000000000010 0000000000000000 0000000000000004 0000000000000000 GPR20: 0000000000000001 c000000002ca2b00 0000000100043bb2 000000000000000a GPR24: 000000000000000a 0000000000000000 0000000000000000 0000000000000000 GPR28: c000000084021d40 c000000084021d50 c0000000be05cd60 c0000000be05cc00 NIP [c000000000961274] blk_mq_complete_request_remote+0x28/0x2d4 LR [c008000009af1808] nvme_loop_queue_response+0x110/0x290 [nvme_loop] Call Trace: 0xc00000000502c640 (unreliable) nvme_loop_queue_response+0x104/0x290 [nvme_loop] __nvmet_req_complete+0x80/0x498 [nvmet] nvmet_req_complete+0x24/0xf8 [nvmet] nvmet_bio_done+0x58/0xcc [nvmet] bio_endio+0x250/0x390 blk_update_request+0x2e8/0x68c blk_mq_end_request+0x30/0x5c lo_complete_rq+0x94/0x110 [loop] blk_complete_reqs+0x78/0x98 handle_softirqs+0x148/0x454 do_softirq_own_stack+0x3c/0x50 __irq_exit_rcu+0x18c/0x1b4 irq_exit+0x1c/0x34 do_IRQ+0x114/0x278 hardware_interrupt_common_virt+0x28c/0x290 Since the queue teardown path already guarantees that all target-side operations have completed, cancelling the tagsets is redundant and unsafe. So avoid cancelling the I/O and admin tagsets during controller reset and shutdown. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Keith Busch <kbusch@kernel.org> |
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst