{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-90099","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-11T19:38:34.786Z","datePublished":"2026-09-17T16:06:10.858Z","dateUpdated":"2026-09-17T16:06:10.858Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-17T16:06:10.858Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: account classifier filter allocations to memcg\n\nAllocations in the tc classifier *_change() paths (filter objects,\nper-CPU counters, and per-filter aux data) use plain GFP_KERNEL without\n__GFP_ACCOUNT, allowing unprivileged users to pin kernel memory outside\nmemcg charging. The shared tcf_exts_init_ex() action array allocation in\ncls_api.c was also uncharged; this patch closes it along with the\nper-classifier filter-object/percpu/aux allocations that remain\nunaccounted.\n\nAdd GFP_KERNEL_ACCOUNT to:\n- the shared tcf_exts_init_ex() action array (cls_api.c), common to every\n  filter of every classifier (32 pointers, 256 bytes);\n- the filter-object, per-CPU-counter, and per-filter aux allocations in\n  cls_basic, cls_bpf, cls_cgroup, cls_flow, cls_flower, cls_fw,\n  cls_matchall, cls_route and cls_u32;\n- the u32_init_knode() replace-path knode allocation (cls_u32.c), which\n  allocates the same struct tc_u_knode + sel.keys on every replace of an\n  existing knode and was missed by the create-path-only conversion.\n\nAlso fix the cls_basic error path: basic_change() inserts fnew into the\nIDR before allocating the per-CPU counter. If alloc_percpu() fails the\nerrout path kfree'd fnew without idr_remove, leaving a dangling pointer\nin the IDR. With GFP_KERNEL_ACCOUNT the percpu alloc becomes failable\non demand (memcg at memory.max), making the dead path attacker-reachable\nand burning the handle permanently. Add the idr_remove on the percpu\nfailure path, matching the basic_set_parms failure-path pattern.\n\nNote: vega@nebusec.ai provided a poc for basic_cls, but it was easy to\nextend to the other classifiers.\n\nConditions to recreate the bug:\n- CONFIG_NET_SCHED, CONFIG_NET_CLS_* (the classifier being used),\n  CONFIG_NET_CLS_ACT, CONFIG_MEMCG, CONFIG_USER_NS, CONFIG_NET_NS.\n- Unprivileged user in a fresh user+network namespace (unshare -Urn),\n  or root with CAP_NET_ADMIN.\n- Create a large number of tc filters (e.g. tc filter add dev lo\n  ingress ... <classifier> ...) while watching a memcg-limited cgroup:\n  system slab grows far faster than memory.current, pinning kernel\n  memory outside memcg charging."}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/cls_api.c","net/sched/cls_basic.c","net/sched/cls_bpf.c","net/sched/cls_cgroup.c","net/sched/cls_flow.c","net/sched/cls_flower.c","net/sched/cls_fw.c","net/sched/cls_matchall.c","net/sched/cls_route.c","net/sched/cls_u32.c"],"versions":[{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","lessThan":"18c68c8f3d3ff0a4def1391021b439c4333a6c71","status":"affected","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","lessThan":"1beb81947eb486716af80db7a584f9e9fef7e003","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/cls_api.c","net/sched/cls_basic.c","net/sched/cls_bpf.c","net/sched/cls_cgroup.c","net/sched/cls_flow.c","net/sched/cls_flower.c","net/sched/cls_fw.c","net/sched/cls_matchall.c","net/sched/cls_route.c","net/sched/cls_u32.c"],"versions":[{"version":"2.6.18","status":"affected"},{"version":"0","lessThan":"2.6.18","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":"2.6.18","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.18","versionEndExcluding":"7.3-rc1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/18c68c8f3d3ff0a4def1391021b439c4333a6c71"},{"url":"https://git.kernel.org/stable/c/1beb81947eb486716af80db7a584f9e9fef7e003"}],"title":"net/sched: account classifier filter allocations to memcg","x_generator":{"engine":"bippy-1.2.0"}}}}