{"id":"CVE-2026-90099","state":"PUBLISHED","title":"net/sched: account classifier filter allocations to memcg","description":"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.","publishedAt":"2026-09-17T16:06:10.858Z","updatedAt":"2026-10-30T12:34:07.767Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"8a622d5b4d81c1572f42bbf3fb823b6e63d44dae","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"5fbb06d4f3d4c509ffe95572384a498bf319e5bf","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"bf6006cea193cf065f7a64fc7974247f8112af33","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"68fb30607169c92de57c5c82b6af8a733af1cc09","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"18c68c8f3d3ff0a4def1391021b439c4333a6c71","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"1beb81947eb486716af80db7a584f9e9fef7e003","versionType":"git"}],"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"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.18","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"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"]}],"references":["https://git.kernel.org/stable/c/8a622d5b4d81c1572f42bbf3fb823b6e63d44dae","https://git.kernel.org/stable/c/5fbb06d4f3d4c509ffe95572384a498bf319e5bf","https://git.kernel.org/stable/c/bf6006cea193cf065f7a64fc7974247f8112af33","https://git.kernel.org/stable/c/68fb30607169c92de57c5c82b6af8a733af1cc09","https://git.kernel.org/stable/c/18c68c8f3d3ff0a4def1391021b439c4333a6c71","https://git.kernel.org/stable/c/1beb81947eb486716af80db7a584f9e9fef7e003"],"weaknesses":[],"ingestedAt":"2026-10-30T12:52:04.348Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/90xxx/CVE-2026-90099.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-90099","state":"PUBLISHED","datePublished":"2026-09-17T16:06:10.858Z","dateUpdated":"2026-10-30T12:34:07.767Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.786Z"},"containers":{"cna":{"title":"net/sched: account classifier filter allocations to memcg","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":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"8a622d5b4d81c1572f42bbf3fb823b6e63d44dae","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"5fbb06d4f3d4c509ffe95572384a498bf319e5bf","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"bf6006cea193cf065f7a64fc7974247f8112af33","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"68fb30607169c92de57c5c82b6af8a733af1cc09","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"18c68c8f3d3ff0a4def1391021b439c4333a6c71","versionType":"git"},{"version":"0da974f4f303a6842516b764507e3c0a03f41e5a","status":"affected","lessThan":"1beb81947eb486716af80db7a584f9e9fef7e003","versionType":"git"}],"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"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.18","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"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"]}],"references":[{"url":"https://git.kernel.org/stable/c/8a622d5b4d81c1572f42bbf3fb823b6e63d44dae"},{"url":"https://git.kernel.org/stable/c/5fbb06d4f3d4c509ffe95572384a498bf319e5bf"},{"url":"https://git.kernel.org/stable/c/bf6006cea193cf065f7a64fc7974247f8112af33"},{"url":"https://git.kernel.org/stable/c/68fb30607169c92de57c5c82b6af8a733af1cc09"},{"url":"https://git.kernel.org/stable/c/18c68c8f3d3ff0a4def1391021b439c4333a6c71"},{"url":"https://git.kernel.org/stable/c/1beb81947eb486716af80db7a584f9e9fef7e003"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:34:07.767Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.18","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.18","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.18","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.18","versionEndExcluding":"6.18.57"},{"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"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}