erofs: handle overlapped pclusters out of crafted images properly
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.1.168, 6.6.72, 6.10.13, 6.11.2
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
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.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- Linux Linux
From 8e6c8fa9f2e95c88a642521a5da19a8e31748846 · fixed in c1172e65aad4b115392ea4c6e61e56e5b9b69df4; From 8e6c8fa9f2e95c88a642521a5da19a8e31748846 · fixed in 1bf7e414cac303c9aec1be67872e19be8b64980c; From 8e6c8fa9f2e95c88a642521a5da19a8e31748846 · fixed in b9b30af0e86ffb485301ecd83b9129c9dfb7ebf8; From 8e6c8fa9f2e95c88a642521a5da19a8e31748846 · fixed in 9cfa199bcbbbba31cbf97b2786f44f4464f3f29a; From 8e6c8fa9f2e95c88a642521a5da19a8e31748846 · fixed in 9e2f9d34dd12e6e5b244ec488bcebd0c2d566c50
- Linux Linux
5.13
- KernelLinux
From 5.13.0 · fixed in 6.1.168; From 6.2.0 · fixed in 6.6.72; From 6.7.0 · fixed in 6.10.13; From 6.11.0 · fixed in 6.11.2