{"id":"CVE-2026-93221","state":"PUBLISHED","title":"nfsd: convert nfsd_net boolean flags to unsigned long flags word","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: convert nfsd_net boolean flags to unsigned long flags word\n\nnfsd_net contains several boolean fields that are accessed from\nconcurrent contexts without serialization.  In particular,\nnfsd4_end_grace() guards its drain path with a plain bool:\n\n    if (nn->grace_ended)\n            return;\n    nn->grace_ended = true;\n\nThe read and the write are independent, and nothing in struct\nnfsd_net serializes them.  At least two contexts can reach this\ncode with no lock held:\n\n    laundromat path\n      laundry_wq kworker\n        nfs4_laundromat()\n          nfsd4_end_grace()\n\n    RECLAIM_COMPLETE path\n      nfsd compound kthread\n        nfsd4_reclaim_complete()\n          inc_reclaim_complete()\n            nfsd4_end_grace()\n\nBoth callers can observe grace_ended == false on different CPUs,\nboth store true, and both proceed into nfsd4_record_grace_done(),\nwhich invokes the active client_tracking_ops->grace_done callback.\nFor tracking ops that drain reclaim_str_hashtbl (legacy_tracking_ops\nvia nfsd4_recdir_purge_old, and the cld v1+ ops via\nnfsd4_cld_grace_done), grace_done calls nfs4_release_reclaim(),\nwhich walks every bucket of reclaim_str_hashtbl with no lock and\ncalls nfs4_remove_reclaim_record() (list_del + kfree) on each\nentry.  Two concurrent walkers corrupt the list and double-free\nevery nfs4_client_reclaim.  A concurrent nfsd4_find_reclaim_client()\niterating the same bucket reads through freed memory.\n\nA third call site exists in nfs4_state_start_net() on the\nskip_grace startup path, but it runs under nfsd_mutex before any\nclient has connected and before the laundromat's first delayed\nwork fires, so it cannot race with the two callers above.\n\nReplace the scattered boolean fields in nfsd_net with a single\nunsigned long flags word and an enum nfsd_net_flag for the bit\npositions.  The grace_ended race is fixed by using\ntest_and_set_bit(), which is atomic on all architectures.  The\nremaining flags (grace_end_forced, in_grace, somebody_reclaimed,\ntrack_reclaim_completes, nfsd_net_up, lockd_up) are converted to\nuse test_bit/set_bit/clear_bit for consistency.  This avoids\nsub-word cmpxchg issues on architectures like Hexagon that only\nsupport word-sized atomic operations.","publishedAt":"2026-09-24T15:10:44.598Z","updatedAt":"2026-10-21T12:52:22.888Z","severity":{"score":8.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"94b450977c60261903c945419d2df4a464de60c4","versionType":"git"},{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"faac245ca739b66e96fb7bb43e21df537239a4e5","versionType":"git"},{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"40bab0da844c142431a6b1cc21b4cf53491dac44","versionType":"git"},{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"df5922fe09a8131c793ffa86adf204999b0470f8","versionType":"git"},{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"11a5fe42e1811f793e04ef885b639ea7668f439d","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/netns.h","fs/nfsd/nfs4proc.c","fs/nfsd/nfs4recover.c","fs/nfsd/nfs4state.c","fs/nfsd/nfsctl.c","fs/nfsd/nfssvc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.2","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.2","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/netns.h","fs/nfsd/nfs4proc.c","fs/nfsd/nfs4recover.c","fs/nfsd/nfs4state.c","fs/nfsd/nfsctl.c","fs/nfsd/nfssvc.c"]}],"references":["https://git.kernel.org/stable/c/94b450977c60261903c945419d2df4a464de60c4","https://git.kernel.org/stable/c/faac245ca739b66e96fb7bb43e21df537239a4e5","https://git.kernel.org/stable/c/40bab0da844c142431a6b1cc21b4cf53491dac44","https://git.kernel.org/stable/c/df5922fe09a8131c793ffa86adf204999b0470f8","https://git.kernel.org/stable/c/11a5fe42e1811f793e04ef885b639ea7668f439d"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/93xxx/CVE-2026-93221.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-93221","state":"PUBLISHED","datePublished":"2026-09-24T15:10:44.598Z","dateUpdated":"2026-10-21T12:52:22.888Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-17T16:02:15.094Z"},"containers":{"cna":{"title":"nfsd: convert nfsd_net boolean flags to unsigned long flags word","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: convert nfsd_net boolean flags to unsigned long flags word\n\nnfsd_net contains several boolean fields that are accessed from\nconcurrent contexts without serialization.  In particular,\nnfsd4_end_grace() guards its drain path with a plain bool:\n\n    if (nn->grace_ended)\n            return;\n    nn->grace_ended = true;\n\nThe read and the write are independent, and nothing in struct\nnfsd_net serializes them.  At least two contexts can reach this\ncode with no lock held:\n\n    laundromat path\n      laundry_wq kworker\n        nfs4_laundromat()\n          nfsd4_end_grace()\n\n    RECLAIM_COMPLETE path\n      nfsd compound kthread\n        nfsd4_reclaim_complete()\n          inc_reclaim_complete()\n            nfsd4_end_grace()\n\nBoth callers can observe grace_ended == false on different CPUs,\nboth store true, and both proceed into nfsd4_record_grace_done(),\nwhich invokes the active client_tracking_ops->grace_done callback.\nFor tracking ops that drain reclaim_str_hashtbl (legacy_tracking_ops\nvia nfsd4_recdir_purge_old, and the cld v1+ ops via\nnfsd4_cld_grace_done), grace_done calls nfs4_release_reclaim(),\nwhich walks every bucket of reclaim_str_hashtbl with no lock and\ncalls nfs4_remove_reclaim_record() (list_del + kfree) on each\nentry.  Two concurrent walkers corrupt the list and double-free\nevery nfs4_client_reclaim.  A concurrent nfsd4_find_reclaim_client()\niterating the same bucket reads through freed memory.\n\nA third call site exists in nfs4_state_start_net() on the\nskip_grace startup path, but it runs under nfsd_mutex before any\nclient has connected and before the laundromat's first delayed\nwork fires, so it cannot race with the two callers above.\n\nReplace the scattered boolean fields in nfsd_net with a single\nunsigned long flags word and an enum nfsd_net_flag for the bit\npositions.  The grace_ended race is fixed by using\ntest_and_set_bit(), which is atomic on all architectures.  The\nremaining flags (grace_end_forced, in_grace, somebody_reclaimed,\ntrack_reclaim_completes, nfsd_net_up, lockd_up) are converted to\nuse test_bit/set_bit/clear_bit for consistency.  This avoids\nsub-word cmpxchg issues on architectures like Hexagon that only\nsupport word-sized atomic operations."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"94b450977c60261903c945419d2df4a464de60c4","versionType":"git"},{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"faac245ca739b66e96fb7bb43e21df537239a4e5","versionType":"git"},{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"40bab0da844c142431a6b1cc21b4cf53491dac44","versionType":"git"},{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"df5922fe09a8131c793ffa86adf204999b0470f8","versionType":"git"},{"version":"362063a595be959bc08f4163e6405a0266740091","status":"affected","lessThan":"11a5fe42e1811f793e04ef885b639ea7668f439d","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/netns.h","fs/nfsd/nfs4proc.c","fs/nfsd/nfs4recover.c","fs/nfsd/nfs4state.c","fs/nfsd/nfsctl.c","fs/nfsd/nfssvc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.2","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.2","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/netns.h","fs/nfsd/nfs4proc.c","fs/nfsd/nfs4recover.c","fs/nfsd/nfs4state.c","fs/nfsd/nfsctl.c","fs/nfsd/nfssvc.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/94b450977c60261903c945419d2df4a464de60c4"},{"url":"https://git.kernel.org/stable/c/faac245ca739b66e96fb7bb43e21df537239a4e5"},{"url":"https://git.kernel.org/stable/c/40bab0da844c142431a6b1cc21b4cf53491dac44"},{"url":"https://git.kernel.org/stable/c/df5922fe09a8131c793ffa86adf204999b0470f8"},{"url":"https://git.kernel.org/stable/c/11a5fe42e1811f793e04ef885b639ea7668f439d"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - nfsd4_end_grace() is reached from a remote NFSv4.1 RECLAIM_COMPLETE: svc_recv to nfsd_dispatch to nfsd4_proc_compound to nfsd4_sequence (sets cstate->clp) to nfsd4_reclaim_complete to inc_reclaim_complete to nfsd4_end_grace on TCP/2049. That RECLAIM_COMPLETE compound is the attacker-supplied protocol message.\nAC:H - The other nfsd4_end_grace() caller is nfs4_laundromat() on laundry_wq, queued in nfs4_state_start_net() for nn->nfsd4_grace seconds. A peer cannot start that work (nfsd4_force_end_grace is only write_v4_end_grace). Both must see grace_ended==false, which needs an already-running grace with a non-empty reclaim_str_hashtbl the attacker cannot create on demand.\nPR:N - Typical nfsd exports accept AUTH_SYS, so the client only asserts a uid. nfsd4_exchange_id() with SP4_NONE and nfsd4_create_session() are ALLOWED_AS_FIRST_OP without a filehandle, and OP_RECLAIM_COMPLETE is ALLOWED_WITHOUT_FH, so no fh_verify, share access, or Kerberos is required.\nUI:N - The attacker sends EXCHANGE_ID, CREATE_SESSION, SEQUENCE, and RECLAIM_COMPLETE on their own session. No write to v4_end_grace, mount, or other victim action is required.\nS:U - Concurrent nfs4_release_reclaim() list_del/kfree of nfs4_client_reclaim entries corrupts heap inside the host nfsd kernel. That stays in the same kernel security authority and is not a VM, IOMMU, or sandbox escape.\nC:H - When two nfsd4_end_grace() callers both run nfsd4_record_grace_done() (nfsd4_cld_grace_done or nfsd4_recdir_purge_old), nfs4_release_reclaim() double-frees every nfs4_client_reclaim while nfsd4_find_reclaim_client() walks the same unlocked cr_strhash bucket through freed objects, a UAF read primitive.\nI:H - nfs4_remove_reclaim_record() does unlocked list_del(&crp->cr_strhash) then kfree on each nfs4_client_reclaim. Two concurrent walkers corrupt adjacent list pointers (unlink write) and double-free the slab objects, which is an arbitrary kernel write.\nA:H - The same unlocked list_del/kfree in nfs4_release_reclaim(), or nfsd4_find_reclaim_client() following a freed cr_strhash, oopses the host kernel (poisoned list pointers or double-free of nfs4_client_reclaim), a full availability loss."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-21T12:52:22.888Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.2","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.2","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.2","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.2","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.2","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}