Bug 2532527 (CVE-2026-89668)

Summary: CVE-2026-89668 kernel: nfsd: move nfsd_debugfs_init() after nfsd4_init_slabs() in init_nfsd()
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 `nfsd` component of the Linux kernel. The `nfsd_debugfs_init()` function is called before `nfsd4_init_slabs()`. If the slab allocation fails, the `nfsd_debugfs_exit()` cleanup function is bypassed, leaving orphaned debugfs files with stale function pointers. This can lead to a use-after-free vulnerability, potentially allowing a local attacker to cause a denial of service or escalate privileges.
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Description OSIDB Bzimport 2026-09-11 23:41:07 UTC 
In the Linux kernel, the following vulnerability has been resolved:

nfsd: move nfsd_debugfs_init() after nfsd4_init_slabs() in init_nfsd()

nfsd_debugfs_init() runs before nfsd4_init_slabs() in init_nfsd().
If the slab allocation fails, the bare "return retval" bypasses
nfsd_debugfs_exit(), leaving orphan debugfs files with stale fops
pointers into the freed module text.

Move nfsd_debugfs_init() to after the slab init succeeds, so the
early return has no debugfs state to clean up.

Since debugfs is now the more recently initialized of the two, also
update the unwind paths to match reverse-initialization (LIFO) order:
run nfsd_debugfs_exit() before nfsd4_free_slabs() in both the
init_nfsd() error path and exit_nfsd(). The nfsd debugfs files only
reference module-global state and have no dependency on the slab
caches, so that reordering is a cleanup with no functional change.
Comment 1 Mauro Matteo Cascella 2026-09-15 10:26:36 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89668.mbox