{"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":"2026-09-17T16:11:13.077Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-17T16:11:13.077Z"},"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-rc1","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-rc1"},{"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"}}}}