{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90326", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.802Z", "datePublished": "2026-09-17T16:08:41.374Z", "dateUpdated": "2026-10-21T12:51:00.266Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-21T12:51:00.266Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblk-cgroup: fix race between policy activation and blkg destruction\n\nWhen switching an IO scheduler on a block device, blkcg_activate_policy()\nallocates blkg_policy_data (pd) for all blkgs attached to the queue.\nHowever, blkcg_activate_policy() may race with concurrent blkcg deletion,\nleading to use-after-free and memory leak issues.\n\nThe use-after-free occurs in the following race:\n\nT1 (blkcg_activate_policy):\n - Successfully allocates pd for blkg1 (loop0->queue, blkcgA)\n - Fails to allocate pd for blkg2 (loop0->queue, blkcgB)\n - Enters the enomem rollback path to release blkg1 resources\n\nT2 (blkcg deletion):\n - blkcgA is deleted concurrently\n - blkg1 is freed via blkg_free_workfn()\n - blkg1->pd is freed\n\nT1 (continued):\n - Rollback path accesses blkg1->pd->online after pd is freed\n - Triggers use-after-free\n\nIn addition, blkg_free_workfn() frees pd before removing the blkg from\nq->blkg_list. This allows blkcg_activate_policy() to allocate a new pd\nfor a blkg that is being destroyed, leaving the newly allocated pd\nunreachable when the blkg is finally freed.\n\nFix these races by extending blkcg_mutex coverage to serialize\nblkcg_activate_policy() rollback and blkg destruction, ensuring pd\nlifecycle is synchronized with blkg list visibility." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The triggering operations are local cgroupfs writes: tg_set_limit() (io.max) or iolatency_set_limit() (io.latency) call blk_throtl_init()/blk_iolatency_init() then blkcg_activate_policy(), while cgroup_rmdir() runs blkcg_css_offline() into blkg_free_workfn(); elv_iosched_store() is an alternate local sysfs path. No remote protocol carries the race inputs.\nAC:L - The attacker drives both sides: one thread writes io.max/io.latency so blkcg_activate_policy() attaches pd without q->blkcg_mutex, while another rmdirs sibling blkcgs so blkg_free_workfn() calls pd_free_fn() on the same blkg->pd[] before list_del. That interleaving does not depend on GFP_KERNEL failure; the documented enomem rollback UAF on pd->online is an extra window the attacker can retry.\nPR:L - tg_set_limit() and iolatency_set_limit() have no capable() check; io.max/io.latency are CFTYPE_NOT_ON_ROOT S_IWUSR files, and blkg_conf_open_bdev() uses blkdev_get_no_open() with no device permission check. A delegated cgroup-v2 subtree owner (typical systemd user slice or rootless container) can write those files and rmdir child cgroups; scheduler sysfs is a stricter alternate path.\nUI:N - The attacker writes io.max/io.latency in cgroups they own and rmdirs those cgroups themselves; no other user must mount a device, open a file, or otherwise participate.\nS:U - The UAF corrupts kernel blkg_policy_data (throtl_grp/iolatency_grp) in the host io controller; impact stays in the kernel's authority and does not cross a VM, IOMMU, or other security boundary.\nC:H - blkg_free_workfn() frees blkg->pd[] while the object remains on q->blkg_list, so blkcg_activate_policy()'s enomem path reads pd->online and pd_offline_fn() (throtl_pd_offline()/tg_flush_bios()) walks the freed throtl_grp; spraying the slab reclaims that object for an arbitrary kernel read.\nI:H - The same freed pd is written (pd->online = false) and passed to pol->pd_free_fn() again (throtl_pd_free() does timer_delete_sync() and call_rcu()), a double-free of throtl_grp/iolatency_grp that yields a kernel write/control-flow primitive.\nA:H - Use-after-free and double-free of blkg_policy_data in blkcg_activate_policy() versus blkg_free_workfn() oops/panic the kernel even when not turned into a full memory primitive." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "block/blk-cgroup.c" ], "versions": [ { "version": "81c1188905f88b77743d1fdeeedfc8cb7b67787d", "lessThan": "b5dae1cd0d8368b4338430ff93403df67f0b8bcc", "status": "affected", "versionType": "git" }, { "version": "bfe46d2efe46c5c952f982e2ca94fe2ec5e58e2a", "lessThan": "083b58373463a6e5ee60ecb135269348f68ad7df", "status": "affected", "versionType": "git" }, { "version": "f1c006f1c6850c14040f8337753a63119bba39b9", "lessThan": "17c18a0df70c2b89ff7fcd74622f1540e98d00fd", "status": "affected", "versionType": "git" }, { "version": "f1c006f1c6850c14040f8337753a63119bba39b9", "lessThan": "91062e3a9ed251726df4e20ff9a1113f1c8ded59", "status": "affected", "versionType": "git" }, { "version": "f1c006f1c6850c14040f8337753a63119bba39b9", "lessThan": "ac34e655dffa74349d885a43d098115336f53842", "status": "affected", "versionType": "git" }, { "version": "f1c006f1c6850c14040f8337753a63119bba39b9", "lessThan": "2cf9f50a38c1839e549a08e22aa35e8d69e2c8fd", "status": "affected", "versionType": "git" }, { "version": "f1c006f1c6850c14040f8337753a63119bba39b9", "lessThan": "5313d4d41739b0cb63000747c97bb1217ac45f3e", "status": "affected", "versionType": "git" }, { "version": "6.1.16", "lessThan": "6.1.17", "status": "affected", "versionType": "semver" }, { "version": "6.2.3", "lessThan": "6.2.4", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "block/blk-cgroup.c" ], "versions": [ { "version": "6.3", "status": "affected" }, { "version": "0", "lessThan": "6.3", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.17", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.2.4", "lessThanOrEqual": "6.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.160", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.114", "lessThanOrEqual": "6.12.*", "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", "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": "6.1.16", "versionEndExcluding": "6.1.17" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2.3", "versionEndExcluding": "6.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "6.6.160" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "6.12.114" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/b5dae1cd0d8368b4338430ff93403df67f0b8bcc" }, { "url": "https://git.kernel.org/stable/c/083b58373463a6e5ee60ecb135269348f68ad7df" }, { "url": "https://git.kernel.org/stable/c/17c18a0df70c2b89ff7fcd74622f1540e98d00fd" }, { "url": "https://git.kernel.org/stable/c/91062e3a9ed251726df4e20ff9a1113f1c8ded59" }, { "url": "https://git.kernel.org/stable/c/ac34e655dffa74349d885a43d098115336f53842" }, { "url": "https://git.kernel.org/stable/c/2cf9f50a38c1839e549a08e22aa35e8d69e2c8fd" }, { "url": "https://git.kernel.org/stable/c/5313d4d41739b0cb63000747c97bb1217ac45f3e" } ], "title": "blk-cgroup: fix race between policy activation and blkg destruction", "x_generator": { "engine": "bippy-1.2.0" } } } }