nilfs2: fix use-after-free bug of ns_writer on remount

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2022-49834
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-05-01 15:16:06 UTC
Updated2026-08-04 10:17:57 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: nilfs2: fix use-after-free bug of ns_writer on remount If a nilfs2 filesystem is downgraded to read-only due to metadata corruption on disk and is remounted read/write, or if emergency read-only remount is performed, detaching a log writer and synchronizing the filesystem can be done at the same time. In these cases, use-after-free of the log writer (hereinafter nilfs->ns_writer) can happen as shown in the scenario below: Task1 Task2 -------------------------------- ------------------------------ nilfs_construct_segment nilfs_segctor_sync init_wait init_waitqueue_entry add_wait_queue schedule nilfs_remount (R/W remount case) nilfs_attach_log_writer nilfs_detach_log_writer nilfs_segctor_destroy kfree finish_wait _raw_spin_lock_irqsave __raw_spin_lock_irqsave do_raw_spin_lock debug_spin_lock_before <-- use-after-free While Task1 is sleeping, nilfs->ns_writer is freed by Task2. After Task1 waked up, Task1 accesses nilfs->ns_writer which is already freed. This scenario diagram is based on the Shigeru Yoshida's post [1]. This patch fixes the issue by not detaching nilfs->ns_writer on remount so that this UAF race doesn't happen. Along with this change, this patch also inserts a few necessary read-only checks with superblock instance where only the ns_writer pointer was used to check if the filesystem is read-only.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-416

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected fe5f171bb272946ce5fbf843ce2f8467d0d41b9a b2fbf10040216ef5ee270773755fc2f5da65b749 git Not specified
CNA Linux Linux affected fe5f171bb272946ce5fbf843ce2f8467d0d41b9a 39a3ed68270b079c6b874d4e4727a512b9b4882c git Not specified
CNA Linux Linux affected fe5f171bb272946ce5fbf843ce2f8467d0d41b9a b4736ab5542112fe0a40f140a0a0b072954f34da git Not specified
CNA Linux Linux affected fe5f171bb272946ce5fbf843ce2f8467d0d41b9a 9b162e81045266a2d5b44df9dffdf05c54de9cca git Not specified
CNA Linux Linux affected fe5f171bb272946ce5fbf843ce2f8467d0d41b9a 4feedde5486c07ea79787839153a71ca71329c7d git Not specified
CNA Linux Linux affected fe5f171bb272946ce5fbf843ce2f8467d0d41b9a afbd1188382a75f6cfe22c0b68533f7f9664f182 git Not specified
CNA Linux Linux affected fe5f171bb272946ce5fbf843ce2f8467d0d41b9a b152300d5a1ba4258dacf9916bff20e6a8c7603b git Not specified
CNA Linux Linux affected fe5f171bb272946ce5fbf843ce2f8467d0d41b9a 8cccf05fe857a18ee26e20d11a8455a73ffd4efd git Not specified
CNA Linux Linux affected 2.6.34 Not specified
CNA Linux Linux unaffected 2.6.34 semver Not specified
CNA Linux Linux unaffected 4.9.334 4.9.* semver Not specified
CNA Linux Linux unaffected 4.14.300 4.14.* semver Not specified
CNA Linux Linux unaffected 4.19.267 4.19.* semver Not specified
CNA Linux Linux unaffected 5.4.225 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.155 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.79 5.15.* semver Not specified
CNA Linux Linux unaffected 6.0.9 6.0.* semver Not specified
CNA Linux Linux unaffected 6.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/afbd1188382a75f6cfe22c0b68533f7f9664f182 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/39a3ed68270b079c6b874d4e4727a512b9b4882c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/b4736ab5542112fe0a40f140a0a0b072954f34da 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/b2fbf10040216ef5ee270773755fc2f5da65b749 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/b152300d5a1ba4258dacf9916bff20e6a8c7603b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/4feedde5486c07ea79787839153a71ca71329c7d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/8cccf05fe857a18ee26e20d11a8455a73ffd4efd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/9b162e81045266a2d5b44df9dffdf05c54de9cca 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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