255 lines
15 KiB
JSON
255 lines
15 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-90326",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-09-11T19:38:34.802Z",
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"datePublished": "2026-09-17T16:08:41.374Z",
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"dateUpdated": "2026-10-21T12:51:00.266Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-10-21T12:51:00.266Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"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."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"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."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"block/blk-cgroup.c"
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],
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"versions": [
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{
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"lessThan": "5313d4d41739b0cb63000747c97bb1217ac45f3e",
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"status": "affected",
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},
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{
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"version": "6.1.16",
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"lessThan": "6.1.17",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "6.2.3",
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"lessThan": "6.2.4",
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"status": "affected",
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}
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"product": "Linux",
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"defaultStatus": "affected",
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"block/blk-cgroup.c"
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],
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"versions": [
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"version": "6.3",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "6.3",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.1.17",
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"lessThanOrEqual": "6.1.*",
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"status": "unaffected",
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},
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{
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"version": "6.2.4",
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"lessThanOrEqual": "6.2.*",
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"status": "unaffected",
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},
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{
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"version": "6.6.160",
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"lessThanOrEqual": "6.6.*",
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"status": "unaffected",
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},
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{
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"version": "6.12.114",
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"lessThanOrEqual": "6.12.*",
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"status": "unaffected",
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},
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{
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"version": "6.18.52",
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"lessThanOrEqual": "6.18.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.2.6",
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"lessThanOrEqual": "7.2.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.3",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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"references": [
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"url": "https://git.kernel.org/stable/c/b5dae1cd0d8368b4338430ff93403df67f0b8bcc"
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},
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"url": "https://git.kernel.org/stable/c/17c18a0df70c2b89ff7fcd74622f1540e98d00fd"
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},
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{
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"url": "https://git.kernel.org/stable/c/91062e3a9ed251726df4e20ff9a1113f1c8ded59"
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},
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{
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"url": "https://git.kernel.org/stable/c/ac34e655dffa74349d885a43d098115336f53842"
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},
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{
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"url": "https://git.kernel.org/stable/c/2cf9f50a38c1839e549a08e22aa35e8d69e2c8fd"
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},
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{
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"url": "https://git.kernel.org/stable/c/5313d4d41739b0cb63000747c97bb1217ac45f3e"
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}
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],
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"title": "blk-cgroup: fix race between policy activation and blkg destruction",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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}
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} |