CVE-2026-90325 (GCVE-0-2026-90325)
Vulnerability from cvelistv5
Published
2026-09-17 16:08
Modified
2026-10-19 09:01
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: skip dying blkg in blkcg_activate_policy() When switching IO schedulers on a block device, blkcg_activate_policy() can race with concurrent blkcg deletion, leading to a use-after-free in rcu_accelerate_cbs. T1: T2: blkg_destroy kill(&blkg->refcnt) // blkg->refcnt=1->0 blkg_release // call_rcu(__blkg_release) ... blkg_free_workfn ->pd_free_fn(pd) elv_iosched_store elevator_switch ... iterate blkg list blkg_get(blkg) // blkg->refcnt=0->1 list_del_init(&blkg->q_node) blkg_put(pinned_blkg) // blkg->refcnt=1->0 blkg_release // call_rcu again rcu_accelerate_cbs // uaf Fix this by checking hlist_unhashed(&blkg->blkcg_node) before getting a reference to the blkg. This is the same check used in blkg_destroy() to detect if a blkg has already been destroyed. If the blkg is already unhashed, skip processing it since it's being destroyed.
References
Impacted products
Vendor Product Version
Linux Linux Version: 81c1188905f88b77743d1fdeeedfc8cb7b67787d
Version: bfe46d2efe46c5c952f982e2ca94fe2ec5e58e2a
Version: f1c006f1c6850c14040f8337753a63119bba39b9
Version: f1c006f1c6850c14040f8337753a63119bba39b9
Version: f1c006f1c6850c14040f8337753a63119bba39b9
Version: f1c006f1c6850c14040f8337753a63119bba39b9
Version: f1c006f1c6850c14040f8337753a63119bba39b9
Version: 6.1.16   ≤
Version: 6.2.3   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "block/blk-cgroup.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "b5dae1cd0d8368b4338430ff93403df67f0b8bcc",
              "status": "affected",
              "version": "81c1188905f88b77743d1fdeeedfc8cb7b67787d",
              "versionType": "git"
            },
            {
              "lessThan": "083b58373463a6e5ee60ecb135269348f68ad7df",
              "status": "affected",
              "version": "bfe46d2efe46c5c952f982e2ca94fe2ec5e58e2a",
              "versionType": "git"
            },
            {
              "lessThan": "1a267295b1ea6a6477963f3fda84adfecd48fcad",
              "status": "affected",
              "version": "f1c006f1c6850c14040f8337753a63119bba39b9",
              "versionType": "git"
            },
            {
              "lessThan": "7337d012ca3fc3a6a2d1c8e2a19c6d97c38b410d",
              "status": "affected",
              "version": "f1c006f1c6850c14040f8337753a63119bba39b9",
              "versionType": "git"
            },
            {
              "lessThan": "3d8c3da95c75a4d312e272fc7b4076dd3ba9115c",
              "status": "affected",
              "version": "f1c006f1c6850c14040f8337753a63119bba39b9",
              "versionType": "git"
            },
            {
              "lessThan": "d8c872901e6459339374e9eea80aa919176c2ccd",
              "status": "affected",
              "version": "f1c006f1c6850c14040f8337753a63119bba39b9",
              "versionType": "git"
            },
            {
              "lessThan": "5e9220389920f33b6a804d50c548cd0cd1b04634",
              "status": "affected",
              "version": "f1c006f1c6850c14040f8337753a63119bba39b9",
              "versionType": "git"
            },
            {
              "lessThan": "6.1.17",
              "status": "affected",
              "version": "6.1.16",
              "versionType": "semver"
            },
            {
              "lessThan": "6.2.4",
              "status": "affected",
              "version": "6.2.3",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "block/blk-cgroup.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.3"
            },
            {
              "lessThan": "6.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.17",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.2.*",
              "status": "unaffected",
              "version": "6.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "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",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.17",
                  "versionStartIncluding": "6.1.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.2.4",
                  "versionStartIncluding": "6.2.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.110",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.52",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblk-cgroup: skip dying blkg in blkcg_activate_policy()\n\nWhen switching IO schedulers on a block device, blkcg_activate_policy()\ncan race with concurrent blkcg deletion, leading to a use-after-free in\nrcu_accelerate_cbs.\n\nT1:                               T2:\n                                  blkg_destroy\n                                  kill(\u0026blkg-\u003erefcnt) // blkg-\u003erefcnt=1-\u003e0\n                                  blkg_release // call_rcu(__blkg_release)\n                                  ...\n                                  blkg_free_workfn\n                                  -\u003epd_free_fn(pd)\nelv_iosched_store\nelevator_switch\n...\niterate blkg list\nblkg_get(blkg) // blkg-\u003erefcnt=0-\u003e1\n                                  list_del_init(\u0026blkg-\u003eq_node)\nblkg_put(pinned_blkg) // blkg-\u003erefcnt=1-\u003e0\nblkg_release // call_rcu again\nrcu_accelerate_cbs // uaf\n\nFix this by checking hlist_unhashed(\u0026blkg-\u003eblkcg_node) before getting\na reference to the blkg. This is the same check used in blkg_destroy()\nto detect if a blkg has already been destroyed. If the blkg is already\nunhashed, skip processing it since it\u0027s being destroyed."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The UAF is reached by writing the local sysfs file /sys/block/\u003cdev\u003e/queue/scheduler (elv_iosched_store \u2192 elevator_switch \u2192 bfq_create_group_hierarchy \u2192 blkcg_activate_policy) or by writing the local cgroup files io.max (tg_set_limit \u2192 blk_throtl_init) or io.latency (iolatency_set_limit \u2192 blk_iolatency_init). No remote protocol carries the triggering state.\nAC:L - The attacker drives both sides: one thread writes io.max/io.latency or queue/scheduler so blkcg_activate_policy() takes the GFP_NOWAIT-fail retry and calls blkg_get() on a q-\u003eblkg_list entry, while another rmdirs a sibling io cgroup so blkcg_css_offline() \u2192 blkg_destroy() kills that blkg\u0027s percpu_ref. The mkdir/write/rmdir cycle can be repeated until the window hits.\nPR:L - cgroup_add_file() creates io.max and io.latency with mode 0644 and current_fsuid(), so an unprivileged user who mkdir\u0027s in a delegated cgroup v2 subtree (systemd user@.service, rootless containers) can write those files and rmdir the cgroup. tg_set_limit()/iolatency_set_limit() have no capability check, and blkg_conf_open_bdev() looks up the disk by MAJ:MIN via blkdev_get_no_open() without opening it.\nUI:N - The attacker performs the mkdir, the io.max/io.latency or scheduler write that enters blkcg_activate_policy(), and the concurrent rmdir that runs blkg_destroy(), all from its own processes; no other user must mount a device or open a file.\nS:U - Double call_rcu on blkg-\u003ercu_head corrupts host-kernel RCU callback lists and the slab-backed blkcg_gq. That stays inside the same kernel security authority and is not a VM, IOMMU, or hypervisor escape.\nC:H - blkcg_activate_policy() calls blkg_get() (percpu_ref_get, not tryget) on a blkg whose refcnt blkg_destroy() already killed, resurrecting it; the matching blkg_put() after mutex_unlock races blkg_free_workfn()\u0027s kfree(blkg) and issues a second call_rcu on the same rcu_head, which the report shows as a UAF in rcu_accelerate_cbs. A UAF on the RCU list and blkcg_gq is an arbitrary kernel-memory read.\nI:H - The second call_rcu(\u0026blkg-\u003ercu_head) from the resurrected blkg_put() corrupts the RCU callback list (rcu_accelerate_cbs) while blkg_free_workfn() still does list_del_init() and pd_free_fn() on that object. Those writes through a freed, sprayable blkcg_gq are a kernel write primitive suitable for control-flow hijack.\nA:H - The commit documents a use-after-free in rcu_accelerate_cbs from the second call_rcu on blkg-\u003ercu_head after blkg_get() resurrects a killed ref; that UAF oopses or panics the kernel even if it is not further exploited."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:01:42.317Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b5dae1cd0d8368b4338430ff93403df67f0b8bcc"
        },
        {
          "url": "https://git.kernel.org/stable/c/083b58373463a6e5ee60ecb135269348f68ad7df"
        },
        {
          "url": "https://git.kernel.org/stable/c/1a267295b1ea6a6477963f3fda84adfecd48fcad"
        },
        {
          "url": "https://git.kernel.org/stable/c/7337d012ca3fc3a6a2d1c8e2a19c6d97c38b410d"
        },
        {
          "url": "https://git.kernel.org/stable/c/3d8c3da95c75a4d312e272fc7b4076dd3ba9115c"
        },
        {
          "url": "https://git.kernel.org/stable/c/d8c872901e6459339374e9eea80aa919176c2ccd"
        },
        {
          "url": "https://git.kernel.org/stable/c/5e9220389920f33b6a804d50c548cd0cd1b04634"
        }
      ],
      "title": "blk-cgroup: skip dying blkg in blkcg_activate_policy()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90325",
    "datePublished": "2026-09-17T16:08:40.710Z",
    "dateReserved": "2026-09-11T19:38:34.802Z",
    "dateUpdated": "2026-10-19T09:01:42.317Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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