CVE-2024-47736: erofs: handle overlapped pclusters out of crafted images properly
Vulnerability summary
CVE-2024-47736 is a medium (CVSS 5.5) Improper Locking vulnerability in linux. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 7.8% of scored vulnerabilities.
Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 14 · Related 16Timeline
- 21-10-2024PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
Description
In 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.
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.18%
Chance of exploitation in the next 30 days
Percentile
8%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.18% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu123 products
- linuxAll versions (No fix recorded) | < 6.8.0-60.63
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 6.8.0-1029.31
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 8e6c8fa9f2e95c88a642521a5da19a8e31748846, < c1172e65aad4b115392ea4c6e61e56e5b9b69df4 | ≥ 8e6c8fa9f2e95c88a642521a5da19a8e31748846, < 1bf7e414cac303c9aec1be67872e19be8b64980c | ≥ 8e6c8fa9f2e95c88a642521a5da19a8e31748846, < b9b30af0e86ffb485301ecd83b9129c9dfb7ebf8 | ≥ 8e6c8fa9f2e95c88a642521a5da19a8e31748846, < 9cfa199bcbbbba31cbf97b2786f44f4464f3f29a | ≥ 8e6c8fa9f2e95c88a642521a5da19a8e31748846, < 9e2f9d34dd12e6e5b244ec488bcebd0c2d566c50 | 5.13
- linux_kernel≥ 5.13, < 6.10.13 | ≥ 6.11, < 6.11.2
Debian1 product
- linux< 6.1.170-1 | < 6.11.2-1
3 vendors · 126 products
