erofs: handle overlapped pclusters out of crafted images properly

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Summary

CVECVE-2024-47736
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-10-21 13:15:03 UTC
Updated2026-04-11 13:16:34 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: erofs: handle overlapped pclusters out of crafted images properly syzbot reported a task hang issue due to a deadlock case where it is waiting for the folio lock of a cached folio that will be used for cache I/Os. After looking into the crafted fuzzed image, I found it's formed with several overlapped big pclusters as below: Ext: logical offset | length : physical offset | length 0: 0.. 16384 | 16384 : 151552.. 167936 | 16384 1: 16384.. 32768 | 16384 : 155648.. 172032 | 16384 2: 32768.. 49152 | 16384 : 537223168.. 537239552 | 16384 ... Here, extent 0/1 are physically overlapped although it's entirely _impossible_ for normal filesystem images generated by mkfs. First, managed folios containing compressed data will be marked as up-to-date and then unlocked immediately (unlike in-place folios) when compressed I/Os are complete. If physical blocks are not submitted in the incremental order, there should be separate BIOs to avoid dependency issues. However, the current code mis-arranges z_erofs_fill_bio_vec() and BIO submission which causes unexpected BIO waits. Second, managed folios will be connected to their own pclusters for efficient inter-queries. However, this is somewhat hard to implement easily if overlapped big pclusters exist. Again, these only appear in fuzzed images so let's simply fall back to temporary short-lived pages for correctness. Additionally, it justifies that referenced managed folios cannot be truncated for now and reverts part of commit 2080ca1ed3e4 ("erofs: tidy up `struct z_erofs_bvec`") for simplicity although it shouldn't be any difference.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

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

Problem Types: CWE-667

CVSS v3.1 Breakdown

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

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 8e6c8fa9f2e95c88a642521a5da19a8e31748846 c1172e65aad4b115392ea4c6e61e56e5b9b69df4 git Not specified
CNA Linux Linux affected 8e6c8fa9f2e95c88a642521a5da19a8e31748846 1bf7e414cac303c9aec1be67872e19be8b64980c git Not specified
CNA Linux Linux affected 8e6c8fa9f2e95c88a642521a5da19a8e31748846 b9b30af0e86ffb485301ecd83b9129c9dfb7ebf8 git Not specified
CNA Linux Linux affected 8e6c8fa9f2e95c88a642521a5da19a8e31748846 9cfa199bcbbbba31cbf97b2786f44f4464f3f29a git Not specified
CNA Linux Linux affected 8e6c8fa9f2e95c88a642521a5da19a8e31748846 9e2f9d34dd12e6e5b244ec488bcebd0c2d566c50 git Not specified
CNA Linux Linux affected 5.13 Not specified
CNA Linux Linux unaffected 5.13 semver Not specified
CNA Linux Linux unaffected 6.1.168 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.72 6.6.* semver Not specified
CNA Linux Linux unaffected 6.10.13 6.10.* semver Not specified
CNA Linux Linux unaffected 6.11.2 6.11.* semver Not specified
CNA Linux Linux unaffected 6.12 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/9e2f9d34dd12e6e5b244ec488bcebd0c2d566c50 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/9cfa199bcbbbba31cbf97b2786f44f4464f3f29a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/c1172e65aad4b115392ea4c6e61e56e5b9b69df4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b9b30af0e86ffb485301ecd83b9129c9dfb7ebf8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/1bf7e414cac303c9aec1be67872e19be8b64980c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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