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-2026-90325",
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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": "2026-09-17T16:08:40.710Z",
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"dateUpdated": "2026-10-19T09:01:42.317Z"
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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": "2026-10-19T09:01:42.317Z"
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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: 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(&blkg->refcnt) // blkg->refcnt=1->0\n blkg_release // call_rcu(__blkg_release)\n ...\n blkg_free_workfn\n ->pd_free_fn(pd)\nelv_iosched_store\nelevator_switch\n...\niterate blkg list\nblkg_get(blkg) // blkg->refcnt=0->1\n list_del_init(&blkg->q_node)\nblkg_put(pinned_blkg) // blkg->refcnt=1->0\nblkg_release // call_rcu again\nrcu_accelerate_cbs // uaf\n\nFix this by checking hlist_unhashed(&blkg->blkcg_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's being destroyed."
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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 UAF is reached by writing the local sysfs file /sys/block/<dev>/queue/scheduler (elv_iosched_store → elevator_switch → bfq_create_group_hierarchy → blkcg_activate_policy) or by writing the local cgroup files io.max (tg_set_limit → blk_throtl_init) or io.latency (iolatency_set_limit → 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->blkg_list entry, while another rmdirs a sibling io cgroup so blkcg_css_offline() → blkg_destroy() kills that blkg's 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's 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->rcu_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()'s 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(&blkg->rcu_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->rcu_head after blkg_get() resurrects a killed ref; that UAF oopses or panics the kernel even if it is not further exploited."
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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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"version": "81c1188905f88b77743d1fdeeedfc8cb7b67787d",
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"lessThan": "b5dae1cd0d8368b4338430ff93403df67f0b8bcc",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "bfe46d2efe46c5c952f982e2ca94fe2ec5e58e2a",
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"lessThan": "083b58373463a6e5ee60ecb135269348f68ad7df",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "f1c006f1c6850c14040f8337753a63119bba39b9",
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"lessThan": "1a267295b1ea6a6477963f3fda84adfecd48fcad",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "f1c006f1c6850c14040f8337753a63119bba39b9",
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"lessThan": "7337d012ca3fc3a6a2d1c8e2a19c6d97c38b410d",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "f1c006f1c6850c14040f8337753a63119bba39b9",
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"lessThan": "3d8c3da95c75a4d312e272fc7b4076dd3ba9115c",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "f1c006f1c6850c14040f8337753a63119bba39b9",
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"lessThan": "d8c872901e6459339374e9eea80aa919176c2ccd",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "f1c006f1c6850c14040f8337753a63119bba39b9",
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"lessThan": "5e9220389920f33b6a804d50c548cd0cd1b04634",
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"status": "affected",
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"versionType": "git"
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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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"versionType": "semver"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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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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"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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"versionType": "semver"
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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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"versionType": "semver"
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},
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{
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"version": "6.6.157",
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"lessThanOrEqual": "6.6.*",
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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": "6.12.110",
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"lessThanOrEqual": "6.12.*",
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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": "6.18.52",
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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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],
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"cpeApplicability": [
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{
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"nodes": [
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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.1.16",
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"versionEndExcluding": "6.1.17"
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/b5dae1cd0d8368b4338430ff93403df67f0b8bcc"
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},
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{
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"url": "https://git.kernel.org/stable/c/083b58373463a6e5ee60ecb135269348f68ad7df"
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},
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{
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"url": "https://git.kernel.org/stable/c/1a267295b1ea6a6477963f3fda84adfecd48fcad"
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},
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{
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"url": "https://git.kernel.org/stable/c/7337d012ca3fc3a6a2d1c8e2a19c6d97c38b410d"
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},
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{
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"url": "https://git.kernel.org/stable/c/3d8c3da95c75a4d312e272fc7b4076dd3ba9115c"
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},
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{
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"url": "https://git.kernel.org/stable/c/d8c872901e6459339374e9eea80aa919176c2ccd"
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},
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{
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"url": "https://git.kernel.org/stable/c/5e9220389920f33b6a804d50c548cd0cd1b04634"
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}
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],
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"title": "blk-cgroup: skip dying blkg in blkcg_activate_policy()",
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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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}
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} |