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mpi3mr_refresh_tgtdevs() and mpi3mr_devinfochg_evt_bh() read tgt_dev->starget and immediately pass it to starget_for_each_device() without holding mrioc->tgtdev_lock. Every writer of this field -- mpi3mr_target_alloc(), mpi3mr_target_destroy(), mpi3mr_slave_destroy() and mpi3mr_sdev_init() -- correctly serializes access under tgtdev_lock, but these two read sites do not, which leaves a check-then-use window against the SCSI core's target teardown path (scsi_remove_target(), invoked e.g. via a concurrent host reset, sysfs "delete", or SCSI EH device offlining running independently of the fwevt workqueue). Sequence observed on production hardware, triggered on the mpi3mr0_fwevt_wrkr workqueue during a SAS topology change shortly after a controller reset: BUG: kernel NULL pointer dereference, address: 0000000000000058 RIP: scsi_is_host_device+0x7/0x20 Call Trace: starget_for_each_device+0x34/0x100 mpi3mr_refresh_tgtdevs+0x152/0x1d0 [mpi3mr] mpi3mr_fwevt_bh+0x514/0x6c0 [mpi3mr] mpi3mr_fwevt_worker+0x1a/0x50 [mpi3mr] process_one_work+0x194/0x380 worker_thread+0x2fe/0x410 mpi3mr_refresh_tgtdevs() reads tgt_dev->starget as non-NULL, but by the time starget_for_each_device() dereferences it, a concurrent mpi3mr_target_destroy() has already cleared tgt_dev->starget under tgtdev_lock and the SCSI/device core has freed the underlying scsi_target (and its embedded struct device). The stale pointer is then walked by dev_to_shost() -> scsi_is_host_device(), producing the NULL/garbage dereference above. Fix this by taking mrioc->tgtdev_lock around every read of tgt_dev->starget, matching the existing writer-side discipline. Since starget_for_each_device() and mpi3mr_update_sdev() can end up doing non-atomic work (e.g. queue_limits_commit_update()), the lock cannot be held across the whole call, so instead pin the target's device with get_device() while holding the lock, drop the lock, then run starget_for_each_device() against the pinned reference and put_device() afterwards. This closes the TOCTOU window instead of merely narrowing it. The same unlocked read-and-dereference pattern also exists earlier in mpi3mr_refresh_tgtdevs()'s first removal-scan loop (tgt_dev->starget->hostdata); fix it the same way by holding tgtdev_lock across that check, which is cheap since it only touches plain struct fields. Assisted-by: Claude:Sonnet5 [Claude Code] Signed-off-by: Laurence Oberman <loberman@redhat.com> Acked-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com> Link: https://patch.msgid.link/20260831120047.14690-1-loberman@redhat.com Signed-off-by: Martin K. Petersen (Oracle) <mkp@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