nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown
In the Linux kernel, the following vulnerability has been resolved: nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown After a DESTROY_SESSION the per-session teardown path can free a session while rpciod still holds an inflight callback rpc_task that dereferences clp->cl_cb_session. nfsd4_probe_callback_sync() flushes cl_callback_wq, but once nfsd4_run_cb_work() has called rpc_call_async() the rpc_task lives on rpciod; flushing the workqueue does not wait for it. rpc_shutdown_client() does drain rpciod tasks, but uses a 1-second wait_event_timeout — tasks stuck in rpc_delay() (e.g. 2-second NFS4ERR_DELAY retries) can outlive the drain. destroy path rpciod ------------ ------ unhash_session(ses) nfsd4_probe_callback_sync(clp) flush_workqueue(cl_callback_wq) /* returns; rpc_task still live */ nfsd4_put_session_locked(ses) free_session(ses) -> kfree(ses) nfsd4_cb_sequence_done() reads cb_clp->cl_cb_session /* freed slab */ A second window exists in nfsd4_process_cb_update(). When __nfsd4_find_backchannel() returns NULL because unhash_session() has already removed the destroyed session from cl_sessions, setup_callback_client() takes the v4.1 early return so clp->cl_cb_session = ses never fires and the field retains a pointer to the about-to-be-freed session. Fix both by converting cl_cb_session to an RCU-protected pointer: - Move the cl_cb_session = ses assignment in setup_callback_client() to after rpc_create() succeeds, so it is only published when a wor
CVE-2026-89708
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-89708
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209",
"lessThan": "2775ec1d617e665eab71ce0f13ab1f7959713a2b",
"versionType": "git"
},
{
"status": "affected",
"version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209",
"lessThan": "f164eb52b6f3cbf40f07fe379f9f421f88e02f76",
"versionType": "git"
},
{
"status": "affected",
"version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209",
"lessThan": "13bdd486c3aad4fc19e6d8b9c3556a4b4c190b25",
"versionType": "git"
},
{
"status": "affected",
"version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209",
"lessThan": "01c5d5f58a5db9b0ee5afba2e49d3157788687b2",
"versionType": "git"
}
],
"programFiles": [
"fs/nfsd/nfs4callback.c",
"fs/nfsd/nfs4state.c",
"fs/nfsd/state.h",
"fs/nfsd/trace.h"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.38"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.38",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.111",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.50",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/nfsd/nfs4callback.c",
"fs/nfsd/nfs4state.c",
"fs/nfsd/state.h",
"fs/nfsd/trace.h"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-89708
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #35190 · Revision 1
- Added to Heist Feed
- Publisher date