{"api_version":"1","generated_at":"2026-09-17T23:17:23+00:00","cve":"CVE-2026-93100","urls":{"html":"https://cve.report/CVE-2026-93100","api":"https://cve.report/api/cve/CVE-2026-93100.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-93100","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-93100"},"summary":{"title":"fs/resctrl: Prevent use-after-free in rdtgroup_kn_put()","description":"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. ]","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-17 17:18:04","updated_at":"2026-09-17 17:18:04"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/4c593c62c1499665baebbb41b70e2c9b7e947b86","name":"https://git.kernel.org/stable/c/4c593c62c1499665baebbb41b70e2c9b7e947b86","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f5bcf539484d2d604c2f2330e09487ea090b21c7","name":"https://git.kernel.org/stable/c/f5bcf539484d2d604c2f2330e09487ea090b21c7","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ae69f936e8ffed553d899ba4c02f8a7461a89e54","name":"https://git.kernel.org/stable/c/ae69f936e8ffed553d899ba4c02f8a7461a89e54","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-93100","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93100","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b8511ccc75c033f6d54188ea4df7bf1e85778740 ae69f936e8ffed553d899ba4c02f8a7461a89e54 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b8511ccc75c033f6d54188ea4df7bf1e85778740 4c593c62c1499665baebbb41b70e2c9b7e947b86 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b8511ccc75c033f6d54188ea4df7bf1e85778740 f5bcf539484d2d604c2f2330e09487ea090b21c7 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected d20edc0bca5577bab38acb5b190619c922ddebf8 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 1b006f8cbde9f3dabdfafe2ff7aa9f831ed5b625 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 40300f986e47dbc8f1d02e5080385f5cf9f85f70 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b5a4949897ebada8132d54c93208989482503103 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.14.170 4.15 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.19.102 4.20 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.4.18 5.5 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.5.2 5.6 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.6","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.6 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.52 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.6 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/resctrl/rdtgroup.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"ae69f936e8ffed553d899ba4c02f8a7461a89e54","status":"affected","version":"b8511ccc75c033f6d54188ea4df7bf1e85778740","versionType":"git"},{"lessThan":"4c593c62c1499665baebbb41b70e2c9b7e947b86","status":"affected","version":"b8511ccc75c033f6d54188ea4df7bf1e85778740","versionType":"git"},{"lessThan":"f5bcf539484d2d604c2f2330e09487ea090b21c7","status":"affected","version":"b8511ccc75c033f6d54188ea4df7bf1e85778740","versionType":"git"},{"status":"affected","version":"d20edc0bca5577bab38acb5b190619c922ddebf8","versionType":"git"},{"status":"affected","version":"1b006f8cbde9f3dabdfafe2ff7aa9f831ed5b625","versionType":"git"},{"status":"affected","version":"40300f986e47dbc8f1d02e5080385f5cf9f85f70","versionType":"git"},{"status":"affected","version":"b5a4949897ebada8132d54c93208989482503103","versionType":"git"},{"lessThan":"4.15","status":"affected","version":"4.14.170","versionType":"semver"},{"lessThan":"4.20","status":"affected","version":"4.19.102","versionType":"semver"},{"lessThan":"5.5","status":"affected","version":"5.4.18","versionType":"semver"},{"lessThan":"5.6","status":"affected","version":"5.5.2","versionType":"semver"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/resctrl/rdtgroup.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.6"},{"lessThan":"5.6","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.52","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.6","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":"6.18.52","versionStartIncluding":"5.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.6","versionStartIncluding":"5.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"5.6","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","vulnerable":true}],"negate":false,"operator":"OR"}]}],"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. ]"}],"providerMetadata":{"dateUpdated":"2026-09-17T16:11:13.077Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"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"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-93100","datePublished":"2026-09-17T16:11:13.077Z","dateReserved":"2026-09-17T16:02:15.085Z","dateUpdated":"2026-09-17T16:11:13.077Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-17 17:18:04","lastModifiedDate":"2026-09-17 17:18:04","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"93100","Ordinal":"1","Title":"fs/resctrl: Prevent use-after-free in rdtgroup_kn_put()","CVE":"CVE-2026-93100","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"93100","Ordinal":"1","NoteData":"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. ]","Type":"Description","Title":"fs/resctrl: Prevent use-after-free in rdtgroup_kn_put()"}]}}}