FKIE_CVE-2026-22980

Vulnerability from fkie_nvd - Published: 2026-01-23 16:15 - Updated: 2026-01-26 15:03
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: provide locking for v4_end_grace Writing to v4_end_grace can race with server shutdown and result in memory being accessed after it was freed - reclaim_str_hashtbl in particularly. We cannot hold nfsd_mutex across the nfsd4_end_grace() call as that is held while client_tracking_op->init() is called and that can wait for an upcall to nfsdcltrack which can write to v4_end_grace, resulting in a deadlock. nfsd4_end_grace() is also called by the landromat work queue and this doesn't require locking as server shutdown will stop the work and wait for it before freeing anything that nfsd4_end_grace() might access. However, we must be sure that writing to v4_end_grace doesn't restart the work item after shutdown has already waited for it. For this we add a new flag protected with nn->client_lock. It is set only while it is safe to make client tracking calls, and v4_end_grace only schedules work while the flag is set with the spinlock held. So this patch adds a nfsd_net field "client_tracking_active" which is set as described. Another field "grace_end_forced", is set when v4_end_grace is written. After this is set, and providing client_tracking_active is set, the laundromat is scheduled. This "grace_end_forced" field bypasses other checks for whether the grace period has finished. This resolves a race which can result in use-after-free.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/06600719d0f7a723811c45e4d51f5b742f345309
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2857bd59feb63fcf40fe4baf55401baea6b4feb4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/34eb22836e0cdba093baac66599d68c4cd245a9d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/53f07d095e7e680c5e4569a55a019f2c0348cdc6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ba4811c8b433bfa681729ca42cc62b6034f223b0
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ca97360860eb02e3ae4ba42c19b439a0fcecbf06
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e8bfa2401d4c51eca6e48e9b33c798828ca9df61
Impacted products
Vendor Product Version
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: provide locking for v4_end_grace\n\nWriting to v4_end_grace can race with server shutdown and result in\nmemory being accessed after it was freed - reclaim_str_hashtbl in\nparticularly.\n\nWe cannot hold nfsd_mutex across the nfsd4_end_grace() call as that is\nheld while client_tracking_op-\u003einit() is called and that can wait for\nan upcall to nfsdcltrack which can write to v4_end_grace, resulting in a\ndeadlock.\n\nnfsd4_end_grace() is also called by the landromat work queue and this\ndoesn\u0027t require locking as server shutdown will stop the work and wait\nfor it before freeing anything that nfsd4_end_grace() might access.\n\nHowever, we must be sure that writing to v4_end_grace doesn\u0027t restart\nthe work item after shutdown has already waited for it.  For this we\nadd a new flag protected with nn-\u003eclient_lock.  It is set only while it\nis safe to make client tracking calls, and v4_end_grace only schedules\nwork while the flag is set with the spinlock held.\n\nSo this patch adds a nfsd_net field \"client_tracking_active\" which is\nset as described.  Another field \"grace_end_forced\", is set when\nv4_end_grace is written.  After this is set, and providing\nclient_tracking_active is set, the laundromat is scheduled.\nThis \"grace_end_forced\" field bypasses other checks for whether the\ngrace period has finished.\n\nThis resolves a race which can result in use-after-free."
    }
  ],
  "id": "CVE-2026-22980",
  "lastModified": "2026-01-26T15:03:51.687",
  "metrics": {},
  "published": "2026-01-23T16:15:54.003",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/06600719d0f7a723811c45e4d51f5b742f345309"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2857bd59feb63fcf40fe4baf55401baea6b4feb4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/34eb22836e0cdba093baac66599d68c4cd245a9d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/53f07d095e7e680c5e4569a55a019f2c0348cdc6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ba4811c8b433bfa681729ca42cc62b6034f223b0"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ca97360860eb02e3ae4ba42c19b439a0fcecbf06"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e8bfa2401d4c51eca6e48e9b33c798828ca9df61"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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