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CVE Record

CVE-2025-21817: block: mark GFP_NOIO around sysfs ->store()

In the Linux kernel, the following vulnerability has been resolved: block: mark GFP_NOIO around sysfs ->store() sysfs ->store is called with queue freezed, meantime we have several ->store() callbacks(update_nr_requests, wbt, scheduler) to allocate memory with GFP_KERNEL which may run into direct reclaim code path, then potential deadlock can be caused. Fix the issue by marking NOIO around sysfs ->store()

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2025-21817 is a Linux kernel block-layer issue that can cause a deadlock when certain sysfs settings are changed while a block queue is frozen. The practical business impact appears to be availability risk, not data theft, based on provided sources. No active exploitation is reported in KEV or the source bundle.

Executive priority

Treat this as a normal-priority kernel availability fix unless affected systems are highly sensitive to storage disruption. It should be included in routine kernel patch cycles, with faster handling for shared infrastructure, storage-heavy hosts, and environments using block tuning automation.

Technical view

The bug is in sysfs ->store() callbacks for block queue settings such as nr_requests, writeback throttling, and scheduler changes. These paths may allocate with GFP_KERNEL while the queue is frozen, entering direct reclaim and causing a potential deadlock. The fix marks the sysfs store path with NOIO behavior.

Likely exposure

Exposure is most likely on Linux systems running kernel builds that include the vulnerable block-layer code and permit changes to relevant block queue sysfs attributes. The provided affected-version data is limited and somewhat ambiguous, so distro-specific kernel advisories should be checked.

Exploitation context

The source describes a potential deadlock triggered through sysfs store operations. It does not describe remote exploitation, privilege requirements, public exploit code, or confirmed in-the-wild abuse. CISA KEV status in the bundle is false.

Researcher notes

The public record lacks CVSS, CWE, exploitability details, and precise distro package mappings. The root cause and fix direction are clear from the kernel description: avoid reclaim-induced deadlock by marking NOIO around block sysfs store operations.

Mitigation direction

  • Review Linux vendor or distribution advisories for CVE-2025-21817.
  • Update to a kernel package that includes the referenced stable fixes.
  • Prioritize systems where local users or automation modify block queue sysfs settings.
  • If patching is delayed, restrict unnecessary write access to block queue sysfs attributes.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and container hosts.
  • Check whether vendor kernel changelogs reference CVE-2025-21817 or the stable commits.
  • Identify scripts or tuning tools that write block queue sysfs settings.
  • Confirm patched systems include the NOIO sysfs store fix from vendor guidance.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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CVE-2025-21817 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
3Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux8985da5481562e96b95e94ed8e5cc9b6565eb82b, c99f66e4084a62a2cc401c4704a84328aeddc9ec, 1645cd7fd42c236c952e9228badcac4fea1829ea, 6.12.96unaffected
LinuxLinux6.13.2unaffected
Weakness

CWE details

No CWE listed

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