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Yehyeong Lee bededeaaef nvme: zero the discard fallback page
nvme_setup_discard() always maps sizeof(struct nvme_dsm_range) *
NVME_DSM_MAX_RANGES = 4096 bytes as the DSM payload however many ranges
the command declares, because some devices ignore the 'Number of Ranges'
field - the Fixes: commit records two that read past the declared ranges.
A single-range discard fills only the first 16 bytes.

Normally the buffer comes from kzalloc() and the other 4080 bytes are
zero.  When that allocation fails the code falls back to the
per-controller ctrl->discard_page, which nvme_init_ctrl() obtains with
alloc_page(GFP_KERNEL) and nothing ever zeroes, so those 4080 bytes are
whatever the page last held and are handed to the controller.  Reaching
it requires the kzalloc(GFP_ATOMIC | __GFP_NOWARN) to fail, that is
memory pressure; it is not remotely triggerable.  Failing the allocation
under KMSAN reproduces it, with the leaked tail full of vmemmap struct
page pointers.  The extent in the report is a partial transfer of the
payload, not the whole 4096 bytes; the 16-byte boundary in it is the one
declared range:

[   11.991601] BUG: KMSAN: uninit-value in dma_map_phys+0x14c8/0x1900
[   11.991969]  dma_map_phys+0x14c8/0x1900
[   11.992220]  dma_map_page_attrs+0xcf/0x130
[   11.992485]  e1000_xmit_frame+0x4099/0x6d10
[   11.992768]  dev_hard_start_xmit+0x22f/0xa80
[   11.993068]  sch_direct_xmit+0x35c/0xcb0
[   11.993315]  __dev_queue_xmit+0x1ee5/0x5eb0
[   11.993608]  ip_finish_output2+0x1903/0x1c30
[   11.993881]  ip_finish_output+0x288/0x870
[   11.994125]  ip_output+0x15e/0x400
[   11.994365]  __ip_queue_xmit+0x1e85/0x1fb0
[   11.994639]  ip_queue_xmit+0x60/0x80
[   11.994899]  __tcp_transmit_skb+0x4e71/0x5fa0
[   11.995210]  tcp_write_xmit+0x3a36/0x9160
[   11.995533]  __tcp_push_pending_frames+0xc5/0x3c0
[   11.995854]  tcp_push+0x7dc/0x840
[   11.996076]  tcp_sendmsg_locked+0x766c/0x8400
[   11.996371]  tcp_sendmsg+0x4b/0x90
[   11.996572]  inet_sendmsg+0x134/0x2a0
[   11.996823]  __sock_sendmsg+0x265/0x360
[   11.997076]  sock_sendmsg+0x100/0x1e0
[   11.997293]  nvme_tcp_try_send+0x196f/0x6370
[   11.997605]  nvme_tcp_queue_rq+0x1d54/0x20b0
[   11.997882]  blk_mq_dispatch_rq_list+0x5ee/0x2e50
[   11.998175]  __blk_mq_sched_dispatch_requests+0x16dc/0x24a0
[   11.998539]  blk_mq_sched_dispatch_requests+0x11b/0x2c0
[   11.998865]  blk_mq_run_work_fn+0x13b/0x280
[   11.999146]  process_scheduled_works+0x966/0x1ad0
[   11.999465]  worker_thread+0xe44/0x1480
[   11.999709]  kthread+0x53b/0x600
[   11.999927]  ret_from_fork+0x29f/0x7c0
[   12.000191]  ret_from_fork_asm+0x1a/0x30
[   12.000460]
[   12.000558] Uninit was created at:
[   12.000788]  __alloc_frozen_pages_noprof+0x8bf/0xd30
[   12.001096]  alloc_pages_mpol+0x1d0/0x5f0
[   12.001326]  alloc_pages_noprof+0x102/0x290
[   12.001627]  nvme_init_ctrl+0x5a3/0x9f0
[   12.001891]  nvme_tcp_create_ctrl+0xd75/0x19b0
[   12.002170]  nvmf_dev_write+0x4c68/0x4fd0
[   12.002426]  vfs_write+0x587/0x1a10
[   12.002636]  __x64_sys_write+0x207/0x4f0
[   12.002874]  x64_sys_call+0x2ff0/0x3ea0
[   12.003123]  do_syscall_64+0x147/0x3b0
[   12.003400]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[   12.003680]
[   12.003777] Bytes 16-2843 of 2844 are uninitialized
[   12.004068] Memory access of size 2844 starts at ffff888109f82000
[   12.004412]
[   12.004530] CPU: 0 UID: 0 PID: 101 Comm: kworker/0:1H Not tainted 7.2.0-rc5-NVMECTL-gf5098b6bae76 #1 PREEMPT(lazy)
[   12.005127] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   12.005762] Workqueue: kblockd blk_mq_run_work_fn
[   12.006073] =====================================================

Allocate the page with __GFP_ZERO.  The single allocation site covers
every use of it: bytes no discard has written stay zero, and bytes one
did write hold that controller's own range list, which it has already
been sent.

Fixes: 530436c45e ("nvme: Discard workaround for non-conformant devices")
Cc: stable@vger.kernel.org
Signed-off-by: Yehyeong Lee <yhlee@isslab.korea.ac.kr>
Signed-off-by: Keith Busch <kbusch@kernel.org>
History 2026-08-10 12:21:30 -07:00
arch CRC updates for 7.2 2026-06-16 09:16:37 +05:30
block block: Make WBT latency writes honor enable state 2026-07-01 19:07:20 -06:00
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto CRC updates for 7.2 2026-06-16 09:16:37 +05:30
Documentation nvmet: add ABI documentation for target configfs interfaces 2026-07-09 10:10:48 -07:00
drivers nvme: zero the discard fallback page 2026-08-10 12:21:30 -07:00
fs for-7.2/block-20260615 2026-06-16 13:02:47 +05:30
include list: Permit context-unguarded access with list_empty_careful() 2026-07-28 10:36:47 -07:00
init Bootconfig updates for v7.2 2026-06-16 17:29:24 +05:30
io_uring for-7.2/block-20260615 2026-06-16 13:02:47 +05:30
ipc kernel-7.2-rc1.misc 2026-06-15 03:05:50 +05:30
kernel block: invalidate cached plug timestamp after task switch 2026-06-16 10:07:36 -06:00
lib Bootconfig updates for v7.2 2026-06-16 17:29:24 +05:30
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm mm/page_io: don't nest queue_lock under rcu in bio_associate_blkg_from_page() 2026-06-24 06:42:31 -06:00
net This update includes the following changes: 2026-06-16 09:01:23 +05:30
rust for-7.2/block-20260615 2026-06-16 13:02:47 +05:30
samples Driver core changes for 7.2-rc1 2026-06-15 12:41:17 +05:30
scripts linux_kselftest-kunit-7.2-rc1 2026-06-16 16:33:57 +05:30
security Kbuild / Kconfig changes for 7.2 2026-06-15 05:01:15 +05:30
sound gpio updates for v7.2-rc1 2026-06-16 07:30:52 +05:30
tools RTLA patches for v7.2 2026-06-16 17:50:34 +05:30
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt vfs-7.2-rc1.misc 2026-06-15 03:59:45 +05:30
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add Askar 2026-04-15 02:15:02 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Rust changes for v7.2 2026-06-15 09:25:48 +05:30
.mailmap MAINTAINERS: update Baoquan He's email address 2026-06-03 16:25:50 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS fbdev fixes & cleanups for 7.2-rc1: 2026-06-16 08:28:41 +05:30
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS MAINTAINERS: add missing NVMe documentation files 2026-07-09 10:10:53 -07:00
Makefile slab changes for 7.2 2026-06-16 08:44:43 +05:30
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

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.


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=========================

* 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
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