{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-89647", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-89647", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-09-11T19:45:38.593Z", "updatedAt": "2026-10-21T12:48:11.164Z", "importedAt": "2026-10-24T01:58:35.090Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "ceph: do not repeat ceph_trim_dentries() if no progress possible", "summary": "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---", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "37c4efc1ddf98ba8b234d116d863a9464445901e", "status": "affected", "versionType": "git", "lessThan": "dd2e9824e5e7dba406005ff779a107f773175a76" }, { "version": "37c4efc1ddf98ba8b234d116d863a9464445901e", "status": "affected", "versionType": "git", "lessThan": "5a541eb401acb89d791da41189d7a79220164b93" }, { "version": "37c4efc1ddf98ba8b234d116d863a9464445901e", "status": "affected", "versionType": "git", "lessThan": "37d6edb2f03b29399a3a337fae78674de51e1695" }, { "version": "37c4efc1ddf98ba8b234d116d863a9464445901e", "status": "affected", "versionType": "git", "lessThan": "3d122b2feb1dd76bb5041bdea5e1e1b007d8d415" }, { "version": "37c4efc1ddf98ba8b234d116d863a9464445901e", "status": "affected", "versionType": "git", "lessThan": "e7d7aa7b730178278109c41fa1b17b06873065d5" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "5.1", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "5.1" }, { "version": "6.6.160", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.109", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.50", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.2.4", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.2.*" }, { "version": "7.3", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }