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erofs: handle overlapped pclusters out of crafted images properly

Linux kernel · CVE-2024-47736
0 news outlets0 CERTs and agencies0 researchers

Assessment: Track

SSVC decision points: exploitation none, automatable no, technical impact partial, deployment high.

What is it?

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 une

Evidence

No coverage recorded yet.

Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
Not scored
EPSS
0.2%
First seen
11 h ago
Status
corroborated

All Linux vulnerabilities