{"api_version":"1","generated_at":"2026-09-11T21:38:11+00:00","cve":"CVE-2026-89647","urls":{"html":"https://cve.report/CVE-2026-89647","api":"https://cve.report/api/cve/CVE-2026-89647.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89647","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89647"},"summary":{"title":"ceph: do not repeat ceph_trim_dentries() if no progress possible","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: do not repeat ceph_trim_dentries() if no progress possible\n\nceph_cap_reclaim_work() re-queues itself for as long as\nceph_trim_dentries() returns -EAGAIN, which happens whenever a lease\nwalk exhausts its `nr_to_scan` budget.  This creates a busy loop that\nconsumes CPU without making any progress when there is nothing to\nreclaim: with no cap pressure (`count==0`) and every scanned lease\nstill valid, each pass runs the full scan budget down to zero and\nreturns `-EAGAIN`, only to be queued again immediately.\n\nThe dir-lease walk made this worse.  When `expire_dir_lease` is\n`false` (i.e. we have no intention of reclaiming dir leases),\n__dir_lease_check() returned `TOUCH` for every valid lease.  `TOUCH`\nmoves the dentry to the tail of the list and resets `di->time` via\n__dentry_dir_lease_touch(), so a walk over N valid leases pointlessly\nrewrote the list, refreshed the timestamps (preventing them from ever\naging out) and always drained `nr_to_scan`, guaranteeing the `-EAGAIN`\nrequeue.\n\nFix this in three steps:\n\n - Return `KEEP` instead of `TOUCH` when `expire_dir_lease` is\n   `false`.  If we are not going to reclaim the lease, leave it in\n   place instead of churning the list and resetting its timestamp; the\n   walk then terminates naturally (or via `STOP` at the first fresh\n   lease).\n\n - Only return `-EAGAIN` from the first (dentry-lease) walk when something\n   was actually freed.  A full batch that frees nothing means retrying\n   the same list immediately is futile; fall through to the dir-lease\n   walk instead.\n\n - After both walks, bail out with success (0) when nothing was freed\n   and there is no cap pressure (`count==0`).  There is no reason to\n   keep retrying when we are not over the cap limit and made no\n   progress.\n\nUnder real cap pressure (`count>0`) the reclaim path is unchanged and\nstill retries via `-EAGAIN`.\n\nWithout this patch, I saw 500 ceph_trim_dentries() calls per second on\nour web servers.  This is very visible in `/proc/lock_stat` (5 minute\ncapture):\n\n              class name    con-bounces    contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg\n\n &mdsc->dentry_list_lock:        126180         128218           0.04        8063.44    15986965.20         124.69        1573354        5296812           0.04        8291.28    74164526.48          14.00\n -----------------------\n &mdsc->dentry_list_lock         111736          [<000000007b11e319>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock           2631          [<0000000050597999>] __dentry_leases_walk+0x64/0x2c8\n &mdsc->dentry_list_lock           3878          [<00000000c0022f62>] __ceph_dentry_lease_touch+0x5c/0xa8\n &mdsc->dentry_list_lock           9973          [<000000002f27cb6f>] __dentry_lease_unlist+0x50/0xa0\n -----------------------\n &mdsc->dentry_list_lock         123621          [<0000000050597999>] __dentry_leases_walk+0x64/0x2c8\n &mdsc->dentry_list_lock           1822          [<000000007b11e319>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock           2720          [<000000002f27cb6f>] __dentry_lease_unlist+0x50/0xa0\n &mdsc->dentry_list_lock             55          [<00000000c0022f62>] __ceph_dentry_lease_touch+0x5c/0xa8\n\nWith this patch:\n\n              class name    con-bounces    contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg\n\n &mdsc->dentry_list_lock:          1203           1215           0.16         408.88       33082.88          27.23        4320501        7357389           0.04         500.64     1961578.00           0.27\n -----------------------\n &mdsc->dentry_list_lock           1029          [<000000003c9aea8a>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock            1\n---truncated---","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:50","updated_at":"2026-09-11 20:19:50"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/37d6edb2f03b29399a3a337fae78674de51e1695","name":"https://git.kernel.org/stable/c/37d6edb2f03b29399a3a337fae78674de51e1695","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/3d122b2feb1dd76bb5041bdea5e1e1b007d8d415","name":"https://git.kernel.org/stable/c/3d122b2feb1dd76bb5041bdea5e1e1b007d8d415","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/5a541eb401acb89d791da41189d7a79220164b93","name":"https://git.kernel.org/stable/c/5a541eb401acb89d791da41189d7a79220164b93","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/e7d7aa7b730178278109c41fa1b17b06873065d5","name":"https://git.kernel.org/stable/c/e7d7aa7b730178278109c41fa1b17b06873065d5","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89647","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89647","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 37c4efc1ddf98ba8b234d116d863a9464445901e 5a541eb401acb89d791da41189d7a79220164b93 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 37c4efc1ddf98ba8b234d116d863a9464445901e 37d6edb2f03b29399a3a337fae78674de51e1695 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 37c4efc1ddf98ba8b234d116d863a9464445901e 3d122b2feb1dd76bb5041bdea5e1e1b007d8d415 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 37c4efc1ddf98ba8b234d116d863a9464445901e e7d7aa7b730178278109c41fa1b17b06873065d5 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.1","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.1 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.109 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.50 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/ceph/dir.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"5a541eb401acb89d791da41189d7a79220164b93","status":"affected","version":"37c4efc1ddf98ba8b234d116d863a9464445901e","versionType":"git"},{"lessThan":"37d6edb2f03b29399a3a337fae78674de51e1695","status":"affected","version":"37c4efc1ddf98ba8b234d116d863a9464445901e","versionType":"git"},{"lessThan":"3d122b2feb1dd76bb5041bdea5e1e1b007d8d415","status":"affected","version":"37c4efc1ddf98ba8b234d116d863a9464445901e","versionType":"git"},{"lessThan":"e7d7aa7b730178278109c41fa1b17b06873065d5","status":"affected","version":"37c4efc1ddf98ba8b234d116d863a9464445901e","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/ceph/dir.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.1"},{"lessThan":"5.1","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.109","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.50","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.109","versionStartIncluding":"5.1","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.50","versionStartIncluding":"5.1","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"5.1","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"5.1","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: do not repeat ceph_trim_dentries() if no progress possible\n\nceph_cap_reclaim_work() re-queues itself for as long as\nceph_trim_dentries() returns -EAGAIN, which happens whenever a lease\nwalk exhausts its `nr_to_scan` budget.  This creates a busy loop that\nconsumes CPU without making any progress when there is nothing to\nreclaim: with no cap pressure (`count==0`) and every scanned lease\nstill valid, each pass runs the full scan budget down to zero and\nreturns `-EAGAIN`, only to be queued again immediately.\n\nThe dir-lease walk made this worse.  When `expire_dir_lease` is\n`false` (i.e. we have no intention of reclaiming dir leases),\n__dir_lease_check() returned `TOUCH` for every valid lease.  `TOUCH`\nmoves the dentry to the tail of the list and resets `di->time` via\n__dentry_dir_lease_touch(), so a walk over N valid leases pointlessly\nrewrote the list, refreshed the timestamps (preventing them from ever\naging out) and always drained `nr_to_scan`, guaranteeing the `-EAGAIN`\nrequeue.\n\nFix this in three steps:\n\n - Return `KEEP` instead of `TOUCH` when `expire_dir_lease` is\n   `false`.  If we are not going to reclaim the lease, leave it in\n   place instead of churning the list and resetting its timestamp; the\n   walk then terminates naturally (or via `STOP` at the first fresh\n   lease).\n\n - Only return `-EAGAIN` from the first (dentry-lease) walk when something\n   was actually freed.  A full batch that frees nothing means retrying\n   the same list immediately is futile; fall through to the dir-lease\n   walk instead.\n\n - After both walks, bail out with success (0) when nothing was freed\n   and there is no cap pressure (`count==0`).  There is no reason to\n   keep retrying when we are not over the cap limit and made no\n   progress.\n\nUnder real cap pressure (`count>0`) the reclaim path is unchanged and\nstill retries via `-EAGAIN`.\n\nWithout this patch, I saw 500 ceph_trim_dentries() calls per second on\nour web servers.  This is very visible in `/proc/lock_stat` (5 minute\ncapture):\n\n              class name    con-bounces    contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg\n\n &mdsc->dentry_list_lock:        126180         128218           0.04        8063.44    15986965.20         124.69        1573354        5296812           0.04        8291.28    74164526.48          14.00\n -----------------------\n &mdsc->dentry_list_lock         111736          [<000000007b11e319>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock           2631          [<0000000050597999>] __dentry_leases_walk+0x64/0x2c8\n &mdsc->dentry_list_lock           3878          [<00000000c0022f62>] __ceph_dentry_lease_touch+0x5c/0xa8\n &mdsc->dentry_list_lock           9973          [<000000002f27cb6f>] __dentry_lease_unlist+0x50/0xa0\n -----------------------\n &mdsc->dentry_list_lock         123621          [<0000000050597999>] __dentry_leases_walk+0x64/0x2c8\n &mdsc->dentry_list_lock           1822          [<000000007b11e319>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock           2720          [<000000002f27cb6f>] __dentry_lease_unlist+0x50/0xa0\n &mdsc->dentry_list_lock             55          [<00000000c0022f62>] __ceph_dentry_lease_touch+0x5c/0xa8\n\nWith this patch:\n\n              class name    con-bounces    contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg\n\n &mdsc->dentry_list_lock:          1203           1215           0.16         408.88       33082.88          27.23        4320501        7357389           0.04         500.64     1961578.00           0.27\n -----------------------\n &mdsc->dentry_list_lock           1029          [<000000003c9aea8a>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock            1\n---truncated---"}],"providerMetadata":{"dateUpdated":"2026-09-11T19:45:38.593Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/5a541eb401acb89d791da41189d7a79220164b93"},{"url":"https://git.kernel.org/stable/c/37d6edb2f03b29399a3a337fae78674de51e1695"},{"url":"https://git.kernel.org/stable/c/3d122b2feb1dd76bb5041bdea5e1e1b007d8d415"},{"url":"https://git.kernel.org/stable/c/e7d7aa7b730178278109c41fa1b17b06873065d5"}],"title":"ceph: do not repeat ceph_trim_dentries() if no progress possible","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89647","datePublished":"2026-09-11T19:45:38.593Z","dateReserved":"2026-09-11T19:38:34.741Z","dateUpdated":"2026-09-11T19:45:38.593Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:50","lastModifiedDate":"2026-09-11 20:19:50","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89647","Ordinal":"1","Title":"ceph: do not repeat ceph_trim_dentries() if no progress possible","CVE":"CVE-2026-89647","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89647","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: do not repeat ceph_trim_dentries() if no progress possible\n\nceph_cap_reclaim_work() re-queues itself for as long as\nceph_trim_dentries() returns -EAGAIN, which happens whenever a lease\nwalk exhausts its `nr_to_scan` budget.  This creates a busy loop that\nconsumes CPU without making any progress when there is nothing to\nreclaim: with no cap pressure (`count==0`) and every scanned lease\nstill valid, each pass runs the full scan budget down to zero and\nreturns `-EAGAIN`, only to be queued again immediately.\n\nThe dir-lease walk made this worse.  When `expire_dir_lease` is\n`false` (i.e. we have no intention of reclaiming dir leases),\n__dir_lease_check() returned `TOUCH` for every valid lease.  `TOUCH`\nmoves the dentry to the tail of the list and resets `di->time` via\n__dentry_dir_lease_touch(), so a walk over N valid leases pointlessly\nrewrote the list, refreshed the timestamps (preventing them from ever\naging out) and always drained `nr_to_scan`, guaranteeing the `-EAGAIN`\nrequeue.\n\nFix this in three steps:\n\n - Return `KEEP` instead of `TOUCH` when `expire_dir_lease` is\n   `false`.  If we are not going to reclaim the lease, leave it in\n   place instead of churning the list and resetting its timestamp; the\n   walk then terminates naturally (or via `STOP` at the first fresh\n   lease).\n\n - Only return `-EAGAIN` from the first (dentry-lease) walk when something\n   was actually freed.  A full batch that frees nothing means retrying\n   the same list immediately is futile; fall through to the dir-lease\n   walk instead.\n\n - After both walks, bail out with success (0) when nothing was freed\n   and there is no cap pressure (`count==0`).  There is no reason to\n   keep retrying when we are not over the cap limit and made no\n   progress.\n\nUnder real cap pressure (`count>0`) the reclaim path is unchanged and\nstill retries via `-EAGAIN`.\n\nWithout this patch, I saw 500 ceph_trim_dentries() calls per second on\nour web servers.  This is very visible in `/proc/lock_stat` (5 minute\ncapture):\n\n              class name    con-bounces    contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg\n\n &mdsc->dentry_list_lock:        126180         128218           0.04        8063.44    15986965.20         124.69        1573354        5296812           0.04        8291.28    74164526.48          14.00\n -----------------------\n &mdsc->dentry_list_lock         111736          [<000000007b11e319>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock           2631          [<0000000050597999>] __dentry_leases_walk+0x64/0x2c8\n &mdsc->dentry_list_lock           3878          [<00000000c0022f62>] __ceph_dentry_lease_touch+0x5c/0xa8\n &mdsc->dentry_list_lock           9973          [<000000002f27cb6f>] __dentry_lease_unlist+0x50/0xa0\n -----------------------\n &mdsc->dentry_list_lock         123621          [<0000000050597999>] __dentry_leases_walk+0x64/0x2c8\n &mdsc->dentry_list_lock           1822          [<000000007b11e319>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock           2720          [<000000002f27cb6f>] __dentry_lease_unlist+0x50/0xa0\n &mdsc->dentry_list_lock             55          [<00000000c0022f62>] __ceph_dentry_lease_touch+0x5c/0xa8\n\nWith this patch:\n\n              class name    con-bounces    contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg\n\n &mdsc->dentry_list_lock:          1203           1215           0.16         408.88       33082.88          27.23        4320501        7357389           0.04         500.64     1961578.00           0.27\n -----------------------\n &mdsc->dentry_list_lock           1029          [<000000003c9aea8a>] __ceph_dentry_dir_lease_touch+0x7c/0xa8\n &mdsc->dentry_list_lock            1\n---truncated---","Type":"Description","Title":"ceph: do not repeat ceph_trim_dentries() if no progress possible"}]}}}