CVE-2026-43076: ocfs2: validate inline data i_size during inode read
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: validate inline data i_size during inode read
When reading an inode from disk, ocfs2_validate_inode_block() performs
various sanity checks but does not validate the size of inline data. If
the filesystem is corrupted, an inode's i_size can exceed the actual
inline data capacity (id_count).
This causes ocfs2_dir_foreach_blk_id() to iterate beyond the inline data
buffer, triggering a use-after-free when accessing directory entries from
freed memory.
In the syzbot report:
- i_size was 1099511627576 bytes (~1TB)
- Actual inline data capacity (id_count) is typically <256 bytes
- A garbage rec_len (54648) caused ctx->pos to jump out of bounds
- This triggered a UAF in ocfs2_check_dir_entry()
Fix by adding a validation check in ocfs2_validate_inode_block() to ensure
inodes with inline data have i_size <= id_count. This catches the
corruption early during inode read and prevents all downstream code from
operating on invalid data.
Security readout for executives and security teams
Plain-English summary
A corrupted OCFS2 filesystem can make the Linux kernel read directory information from memory that has already been freed. Processing such a filesystem may crash the system or compromise data confidentiality and integrity. Exploitation requires local interaction with a crafted or corrupted filesystem; this is not described as a remotely reachable flaw.
Executive priority
Prioritize systems that actively use OCFS2 or accept filesystem images from less-trusted sources. Patch those systems promptly through supported kernel channels. Systems without OCFS2 exposure have lower immediate urgency, but teams should verify configuration rather than assume safety. No active exploitation is established by the supplied evidence.
Technical view
OCFS2 inode validation failed to ensure inline-data i_size was no larger than id_count. An oversized value could drive directory iteration beyond the inline buffer and cause a use-after-free in ocfs2_check_dir_entry(). The fix rejects malformed inline-data inodes during inode reading before downstream processing.
Likely exposure
Exposure is concentrated on Linux systems using OCFS2 that may mount or process corrupted or attacker-influenced filesystems. The supplied CVSS vector indicates local access, low complexity, no privileges, and required user interaction. Branch-specific affected status is complex, so deployed kernels should be checked against vendor advisories or the cited stable commits.
Exploitation context
The issue was found through syzbot using a malformed inode with an approximately 1 TB i_size despite under 256 bytes of inline capacity. The supplied record is not in KEV and provides no evidence of active exploitation. It does not establish reliable code execution; the documented result is a kernel use-after-free.
Researcher notes
The failure originates in ocfs2_dir_foreach_blk_id() after malformed inline-data metadata bypasses inode validation. The reported garbage rec_len moved ctx->pos out of bounds, producing a use-after-free in ocfs2_check_dir_entry(). The patch adds the invariant i_size <= id_count for inline data. The bundle provides multiple stable-branch commits but no exploitability analysis beyond the syzbot crash.
Mitigation direction
Install a vendor-supported kernel containing the applicable OCFS2 validation fix.
Check distribution guidance to map the fix to each deployed kernel branch.
Avoid mounting untrusted or unexplained OCFS2 media until affected systems are updated.
Restrict filesystem-mounting capabilities and access to OCFS2 storage where operationally feasible.
Validation and detection
Inventory systems with OCFS2 enabled, mounted, or used for removable and shared storage.
Record kernel package versions and compare them with distribution security advisories.
Confirm the applicable stable fix commit is present in custom kernel builds.
After updating, verify systems boot normally and required OCFS2 volumes mount successfully.
Review kernel logs for OCFS2 corruption warnings, crashes, or memory-safety reports.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
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CVSS vector scores
1 official score
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