CVE-2021-46988 (GCVE-0-2021-46988)
Vulnerability from cvelistv5 – Published: 2024-02-28 08:13 – Updated: 2026-05-11 13:45
VLAI
EPSS
VEX
Title
userfaultfd: release page in error path to avoid BUG_ON
Summary
In the Linux kernel, the following vulnerability has been resolved:
userfaultfd: release page in error path to avoid BUG_ON
Consider the following sequence of events:
1. Userspace issues a UFFD ioctl, which ends up calling into
shmem_mfill_atomic_pte(). We successfully account the blocks, we
shmem_alloc_page(), but then the copy_from_user() fails. We return
-ENOENT. We don't release the page we allocated.
2. Our caller detects this error code, tries the copy_from_user() after
dropping the mmap_lock, and retries, calling back into
shmem_mfill_atomic_pte().
3. Meanwhile, let's say another process filled up the tmpfs being used.
4. So shmem_mfill_atomic_pte() fails to account blocks this time, and
immediately returns - without releasing the page.
This triggers a BUG_ON in our caller, which asserts that the page
should always be consumed, unless -ENOENT is returned.
To fix this, detect if we have such a "dangling" page when accounting
fails, and if so, release it before returning.
Severity
No CVSS data available.
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-06-21 16:28 UTC
Assigner
References
7 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
cb658a453b9327ce96ce5222c24d162b5b65b564 , < 319116227e52d49eee671f0aa278bac89b3c1b69
(git)
Affected: cb658a453b9327ce96ce5222c24d162b5b65b564 , < 07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f (git) Affected: cb658a453b9327ce96ce5222c24d162b5b65b564 , < b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43 (git) Affected: cb658a453b9327ce96ce5222c24d162b5b65b564 , < 140cfd9980124aecb6c03ef2e69c72d0548744de (git) Affected: cb658a453b9327ce96ce5222c24d162b5b65b564 , < ad53127973034c63b5348715a1043d0e80ceb330 (git) Affected: cb658a453b9327ce96ce5222c24d162b5b65b564 , < 2d59a0ed8b26b8f3638d8afc31f839e27759f1f6 (git) Affected: cb658a453b9327ce96ce5222c24d162b5b65b564 , < 7ed9d238c7dbb1fdb63ad96a6184985151b0171c (git) |
guessed | |
| Linux | Linux |
Affected:
4.11
Unaffected: 0 , < 4.11 (semver) Unaffected: 4.14.233 , ≤ 4.14.* (semver) Unaffected: 4.19.191 , ≤ 4.19.* (semver) Unaffected: 5.4.120 , ≤ 5.4.* (semver) Unaffected: 5.10.38 , ≤ 5.10.* (semver) Unaffected: 5.11.22 , ≤ 5.11.* (semver) Unaffected: 5.12.5 , ≤ 5.12.* (semver) Unaffected: 5.13 , ≤ * (original_commit_for_fix) |
guessed |
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.