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CVE-2026-22980

nfsd: provide locking for v4_end_grace

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.248, 5.15.198, 6.1.161, 6.6.121, 6.12.66, and 1 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 · fixed in ca97360860eb02e3ae4ba42c19b439a0fcecbf06; From 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 · fixed in e8bfa2401d4c51eca6e48e9b33c798828ca9df61; From 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 · fixed in 34eb22836e0cdba093baac66599d68c4cd245a9d; From 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 · fixed in 06600719d0f7a723811c45e4d51f5b742f345309; From 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 · fixed in ba4811c8b433bfa681729ca42cc62b6034f223b0; From 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 · fixed in 53f07d095e7e680c5e4569a55a019f2c0348cdc6; From 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 · fixed in 2857bd59feb63fcf40fe4baf55401baea6b4feb4

  • Linux Linux

    3.18

  • KernelLinux

    From 3.18.0 · fixed in 5.10.248; From 5.11.0 · fixed in 5.15.198; From 5.16.0 · fixed in 6.1.161; From 6.2.0 · fixed in 6.6.121; From 6.7.0 · fixed in 6.12.66; From 6.13.0 · fixed in 6.18.6

References 7

git.kernel.org