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3086c49a07
ntfs_sd_add_everyone() builds the on-disk security descriptor for a
newly created file by kmalloc()'ing a buffer and then partially
filling it in:
sd = kmalloc(sd_len, GFP_NOFS);
...
sd->revision = 1;
sd->control = SE_DACL_PRESENT | SE_SELF_RELATIVE;
...
The buffer is then handed to ntfs_attr_add() and persisted as the
SECURITY_DESCRIPTOR attribute of the new MFT record. The descriptor
covers a relative security descriptor header, two SIDs (owner and
group), an ACL header, and a single ACE, but several fields inside
those structures are never written before the buffer is committed
to disk:
- struct security_descriptor_relative
@alignment (1 byte)
@sacl (4 bytes; SE_SACL_PRESENT is not set
but the offset still reaches disk)
- struct ntfs_sid (3 instances: owner, group, ACE.sid)
identifier_authority.value[0..4] (5 bytes per SID, 15 total
- only value[5] is set)
- struct ntfs_acl
@alignment1 (1 byte)
@alignment2 (2 bytes)
That is 23 bytes of uninitialised slab memory persisted to disk for
every new file or directory the legacy ntfs driver creates. The
"+ 4" trailing accounting in sd_len holds ace->sid.sub_authority[0],
which the existing code does explicitly write to zero, so it is
not part of the leak.
Anything later able to read the SECURITY_DESCRIPTOR attribute - the
same NTFS volume mounted on Windows or by another NTFS reader, an
offline forensics tool, an unprivileged user that ends up with read
access to the volume - can recover those bytes. The leak persists
for the lifetime of the file on disk, not just the lifetime of the
kernel that wrote it.
Switch the allocation to kzalloc() so every byte the on-disk
descriptor covers is zero before the explicit initialisations run.
While there, replace the bare "return -1" allocation-failure path
with a proper -ENOMEM so the error reaches userspace as a meaningful
errno instead of an unrelated -EPERM.
Found by inspection while auditing fs/ntfs new-inode paths.
Fixes:
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History
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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. 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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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