{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-93100", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-17T16:02:15.085Z", "datePublished": "2026-09-17T16:11:13.077Z", "dateUpdated": "2026-10-19T09:05:33.305Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:05:33.305Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/resctrl: Prevent use-after-free in rdtgroup_kn_put()\n\nA struct rdtgroup is reference counted via rdtgroup::waitcount. Callers that\nneed the structure to remain valid across a sleep (while waiting on acquiring\nrdtgroup_mutex) take a reference with rdtgroup_kn_get() and release it with\nrdtgroup_kn_put().\n\nThe release path is intended to serve as the fallback freer: if the count\ndrops to zero and the group has already been marked RDT_DELETED,\nrdtgroup_kn_put() frees the structure.\n\nThe bulk teardown paths free_all_child_rdtgrp() and rmdir_all_sub() resulting\nfrom a resctrl directory remove or resctrl fs unmount act as the primary\nfreer: they hold rdtgroup_mutex and free each rdtgroup whose waitcount is\nzero, otherwise they set RDT_DELETED and leave the freeing to the last waiter.\n\nThese two freers race. rdtgroup_kn_put() commits waitcount == 0 with\natomic_dec_and_test() outside rdtgroup_mutex, then reads rdtgroup::flags.\nBetween those two operations a concurrent caller of free_all_child_rdtgrp()\nor rmdir_all_sub() (which holds the mutex) can observe waitcount == 0 via\natomic_read(), call rdtgroup_remove(), and kfree() the structure.\n\nThe subsequent read of rdtgroup::flags in rdtgroup_kn_put() is then\na use-after-free, and the structure may even be freed twice if the freed\nmemory happens to satisfy the RDT_DELETED flag check.\n\nReplace the bare atomic_dec_and_test() with atomic_dec_and_mutex_lock() so\nthat the decrement-to-zero takes rdtgroup_mutex before the count becomes\nglobally visible. The inspection of rdtgroup::flags then runs under the same\nmutex held by the bulk freers, making the two paths mutually exclusive.\n\nThe common case where the count does not reach zero remains lock-free. Defer\nkernfs_unbreak_active_protection() until after the mutex is dropped since\nkernfs active protections functionally wrap rdtgroup_mutex. Remove resource\ngroup, which in turn drops its kernfs reference, after kernfs protection is\nrestored.\n\n [ bp: Split the commit messsages into smaller, easier-parseable paragraphs. ]" } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/resctrl/rdtgroup.c" ], "versions": [ { "version": "b8511ccc75c033f6d54188ea4df7bf1e85778740", "lessThan": "ae69f936e8ffed553d899ba4c02f8a7461a89e54", "status": "affected", "versionType": "git" }, { "version": "b8511ccc75c033f6d54188ea4df7bf1e85778740", "lessThan": "4c593c62c1499665baebbb41b70e2c9b7e947b86", "status": "affected", "versionType": "git" }, { "version": "b8511ccc75c033f6d54188ea4df7bf1e85778740", "lessThan": "f5bcf539484d2d604c2f2330e09487ea090b21c7", "status": "affected", "versionType": "git" }, { "version": "d20edc0bca5577bab38acb5b190619c922ddebf8", "status": "affected", "versionType": "git" }, { "version": "1b006f8cbde9f3dabdfafe2ff7aa9f831ed5b625", "status": "affected", "versionType": "git" }, { "version": "40300f986e47dbc8f1d02e5080385f5cf9f85f70", "status": "affected", "versionType": "git" }, { "version": "b5a4949897ebada8132d54c93208989482503103", "status": "affected", "versionType": "git" }, { "version": "4.14.170", "lessThan": "4.15", "status": "affected", "versionType": "semver" }, { "version": "4.19.102", "lessThan": "4.20", "status": "affected", "versionType": "semver" }, { "version": "5.4.18", "lessThan": "5.5", "status": "affected", "versionType": "semver" }, { "version": "5.5.2", "lessThan": "5.6", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/resctrl/rdtgroup.c" ], "versions": [ { "version": "5.6", "status": "affected" }, { "version": "0", "lessThan": "5.6", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.52", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.6", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.6", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.6", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.6", "versionEndExcluding": "7.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.14.170" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19.102" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.4.18" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/ae69f936e8ffed553d899ba4c02f8a7461a89e54" }, { "url": "https://git.kernel.org/stable/c/4c593c62c1499665baebbb41b70e2c9b7e947b86" }, { "url": "https://git.kernel.org/stable/c/f5bcf539484d2d604c2f2330e09487ea090b21c7" } ], "title": "fs/resctrl: Prevent use-after-free in rdtgroup_kn_put()", "x_generator": { "engine": "bippy-1.2.0" } } } }