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CVE Record

CVE-2021-47483: regmap: Fix possible double-free in regcache_rbtree_exit()

In the Linux kernel, the following vulnerability has been resolved: regmap: Fix possible double-free in regcache_rbtree_exit() In regcache_rbtree_insert_to_block(), when 'present' realloc failed, the 'blk' which is supposed to assign to 'rbnode->block' will be freed, so 'rbnode->block' points a freed memory, in the error handling path of regcache_rbtree_init(), 'rbnode->block' will be freed again in regcache_rbtree_exit(), KASAN will report double-free as follows: BUG: KASAN: double-free or invalid-free in kfree+0xce/0x390 Call Trace: slab_free_freelist_hook+0x10d/0x240 kfree+0xce/0x390 regcache_rbtree_exit+0x15d/0x1a0 regcache_rbtree_init+0x224/0x2c0 regcache_init+0x88d/0x1310 __regmap_init+0x3151/0x4a80 __devm_regmap_init+0x7d/0x100 madera_spi_probe+0x10f/0x333 [madera_spi] spi_probe+0x183/0x210 really_probe+0x285/0xc30 To fix this, moving up the assignment of rbnode->block to immediately after the reallocation has succeeded so that the data structure stays valid even if the second reallocation fails.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel memory management bug in the regmap cache code. Under a failed memory reallocation during device initialization, the kernel could free the same memory twice. The sources do not provide CVSS, confirmed exploitation, or a clear business-impact rating.

Executive priority

Treat as a kernel maintenance and reliability issue until stronger exploit evidence appears. Prioritize normal patch cycles, with faster action for appliances, embedded Linux, or hardware-dependent systems matching affected kernels.

Technical view

The flaw is a double-free in regcache_rbtree_exit() after regcache_rbtree_insert_to_block() handles a failed reallocation incorrectly. The fix moves rbnode->block assignment immediately after successful reallocation so cleanup paths see a valid structure state.

Likely exposure

Exposure is limited to Linux kernels in the affected version data and systems reaching this regmap rbtree cache initialization path, likely through affected hardware driver probing. Distribution backports may change version-based conclusions.

Exploitation context

The source bundle reports KASAN detecting double-free or invalid-free during kernel driver probe error handling. It does not cite public exploitation, CISA KEV listing, exploit availability, privilege requirements, or remote attack conditions.

Researcher notes

Evidence supports a cleanup-path double-free caused by inconsistent rbnode->block state after allocation failure. The affected-version notation is sparse and should be reconciled against exact vendor kernel trees and backported commits.

Mitigation direction

  • Check Linux vendor advisories for CVE-2021-47483 coverage.
  • Upgrade to a kernel containing the referenced stable fixes.
  • Confirm distribution backports before relying on upstream version numbers.
  • Prioritize systems with regmap-backed device drivers if exposure is confirmed.
  • If no patch is available, request vendor mitigation guidance.

Validation and detection

  • Inventory running kernel versions across Linux assets.
  • Compare kernels against vendor advisories and affected source data.
  • Verify package changelogs mention CVE-2021-47483 or referenced commits.
  • Review crash logs for regcache_rbtree_exit() double-free signatures.
  • Confirm updated kernels boot and affected drivers initialize normally.
Prepared
Confidence
medium
Sources
10

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2021-47483 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
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux3f4ff561bc88b074d5e868dde4012d89cbb06c87, 3f4ff561bc88b074d5e868dde4012d89cbb06c87, 3f4ff561bc88b074d5e868dde4012d89cbb06c87, 3f4ff561bc88b074d5e868dde4012d89cbb06c87, 3f4ff561bc88b074d5e868dde4012d89cbb06c87, 3f4ff561bc88b074d5e868dde4012d89cbb06c87, 3f4ff561bc88b074d5e868dde4012d89cbb06c87, 3f4ff561bc88b074d5e868dde4012d89cbb06c87unaffected
LinuxLinux3.12, 0, 4.4.291, 4.9.289, 4.14.254, 4.19.215, 5.4.157, 5.10.77, 5.14.16, 5.15affected
Weakness

CWE details

No CWE listed

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