CVE-2026-90099

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: account classifier filter allocations to memcg Allocations in the tc classifier *_change() paths (filter objects, per-CPU counters, and per-filter aux data) use plain GFP_KERNEL without __GFP_ACCOUNT, allowing unprivileged users to pin kernel memory outside memcg charging. The shared tcf_exts_init_ex() action array allocation in cls_api.c was also uncharged; this patch closes it along with the per-classifier filter-object/percpu/aux allocations that remain unaccounted. Add GFP_KERNEL_ACCOUNT to: - the shared tcf_exts_init_ex() action array (cls_api.c), common to every filter of every classifier (32 pointers, 256 bytes); - the filter-object, per-CPU-counter, and per-filter aux allocations in cls_basic, cls_bpf, cls_cgroup, cls_flow, cls_flower, cls_fw, cls_matchall, cls_route and cls_u32; - the u32_init_knode() replace-path knode allocation (cls_u32.c), which allocates the same struct tc_u_knode + sel.keys on every replace of an existing knode and was missed by the create-path-only conversion. Also fix the cls_basic error path: basic_change() inserts fnew into the IDR before allocating the per-CPU counter. If alloc_percpu() fails the errout path kfree'd fnew without idr_remove, leaving a dangling pointer in the IDR. With GFP_KERNEL_ACCOUNT the percpu alloc becomes failable on demand (memcg at memory.max), making the dead path attacker-reachable and burning the handle permanently. Add the idr_remove on the percpu failure path, matching the basic_set_parms failure-path pattern. Note: [email protected] provided a poc for basic_cls, but it was easy to extend to the other classifiers. Conditions to recreate the bug: - CONFIG_NET_SCHED, CONFIG_NET_CLS_* (the classifier being used), CONFIG_NET_CLS_ACT, CONFIG_MEMCG, CONFIG_USER_NS, CONFIG_NET_NS. - Unprivileged user in a fresh user+network namespace (unshare -Urn), or root with CAP_NET_ADMIN. - Create a large number of tc filters (e.g. tc filter add dev lo ingress ... <classifier> ...) while watching a memcg-limited cgroup: system slab grows far faster than memory.current, pinning kernel memory outside memcg charging.

Severity

Not scored

CVSS score

Not available

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-17 17:17:01.567000

Last modified

2026-10-30 13:20:41.400000

View original CVE JSON

{
  "id": "CVE-2026-90099",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-17T17:17:01.567",
  "lastModified": "2026-10-30T13:20:41.400",
  "vulnStatus": "Received",
  "cveTags": [],
  "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: [email protected] 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": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "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"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "0da974f4f303a6842516b764507e3c0a03f41e5a",
              "lessThan": "8a622d5b4d81c1572f42bbf3fb823b6e63d44dae",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "0da974f4f303a6842516b764507e3c0a03f41e5a",
              "lessThan": "5fbb06d4f3d4c509ffe95572384a498bf319e5bf",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "0da974f4f303a6842516b764507e3c0a03f41e5a",
              "lessThan": "bf6006cea193cf065f7a64fc7974247f8112af33",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "0da974f4f303a6842516b764507e3c0a03f41e5a",
              "lessThan": "68fb30607169c92de57c5c82b6af8a733af1cc09",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "0da974f4f303a6842516b764507e3c0a03f41e5a",
              "lessThan": "18c68c8f3d3ff0a4def1391021b439c4333a6c71",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "0da974f4f303a6842516b764507e3c0a03f41e5a",
              "lessThan": "1beb81947eb486716af80db7a584f9e9fef7e003",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "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"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "2.6.18",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "2.6.18",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.160",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.114",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.57",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.6",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {},
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/18c68c8f3d3ff0a4def1391021b439c4333a6c71",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/1beb81947eb486716af80db7a584f9e9fef7e003",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/5fbb06d4f3d4c509ffe95572384a498bf319e5bf",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/68fb30607169c92de57c5c82b6af8a733af1cc09",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/8a622d5b4d81c1572f42bbf3fb823b6e63d44dae",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/bf6006cea193cf065f7a64fc7974247f8112af33",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}