Bug 2554894 (CVE-2026-98443)

Summary: CVE-2026-98443 kernel: xfs: fix cursor and pointer handling when recovering iunlink buckets
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's XFS file system. Improper pointer handling during the recovery of unlinked files can cause a use-after-free condition, where the operating system attempts to access memory after it has already been freed. A local user capable of mounting a specially crafted file system could exploit this vulnerability during recovery operations, leading to memory corruption or a system crash resulting in a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-10-18 15:26:12 UTC 
In the Linux kernel, the following vulnerability has been resolved:

xfs: fix cursor and pointer handling when recovering iunlink buckets

LOLLM pointed out a bug in xlog_recover_iunlink_bucket:

1. We don't null out prev_ip after releasing it, which can lead to UAF
   problems if the inodegc flush call in the loop fails.

at which point I noticed even more bugs:

2. If the inodegc flush inside the loop fails, we also leak @ip.

3. We set prev_agino to agino having already advanced agino, which
   results in inodes with i_prev_unlinked set to itself.

4. If we exit the bottom of the loop with prev_ip set, then prev_ip
   aliases ip and we also set its i_prev_unlinked to itself.

Bugs 3 and 4 introduce loops into the unlinked list, though these loops
don't surface because we immediately flush each unlinked inode after
loading it.

Fix all of these issues.
Comment 1 Mauro Matteo Cascella 2026-10-19 11:37:22 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98443.mbox