{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2025-68807",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2025-12-24T10:30:51.045Z",
        "datePublished": "2026-01-13T15:29:14.483Z",
        "dateUpdated": "2026-05-11T21:53:43.171Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-05-11T21:53:43.171Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblock: fix race between wbt_enable_default and IO submission\n\nWhen wbt_enable_default() is moved out of queue freezing in elevator_change(),\nit can cause the wbt inflight counter to become negative (-1), leading to hung\ntasks in the writeback path. Tasks get stuck in wbt_wait() because the counter\nis in an inconsistent state.\n\nThe issue occurs because wbt_enable_default() could race with IO submission,\nallowing the counter to be decremented before proper initialization. This manifests\nas:\n\n  rq_wait[0]:\n    inflight:             -1\n    has_waiters:        True\n\nrwb_enabled() checks the state, which can be updated exactly between wbt_wait()\n(rq_qos_throttle()) and wbt_track()(rq_qos_track()), then the inflight counter\nwill become negative.\n\nAnd results in hung task warnings like:\n  task:kworker/u24:39 state:D stack:0 pid:14767\n  Call Trace:\n    rq_qos_wait+0xb4/0x150\n    wbt_wait+0xa9/0x100\n    __rq_qos_throttle+0x24/0x40\n    blk_mq_submit_bio+0x672/0x7b0\n    ...\n\nFix this by:\n\n1. Splitting wbt_enable_default() into:\n   - __wbt_enable_default(): Returns true if wbt_init() should be called\n   - wbt_enable_default(): Wrapper for existing callers (no init)\n   - wbt_init_enable_default(): New function that checks and inits WBT\n\n2. Using wbt_init_enable_default() in blk_register_queue() to ensure\n   proper initialization during queue registration\n\n3. Move wbt_init() out of wbt_enable_default() which is only for enabling\n   disabled wbt from bfq and iocost, and wbt_init() isn't needed. Then the\n   original lock warning can be avoided.\n\n4. Removing the ELEVATOR_FLAG_ENABLE_WBT_ON_EXIT flag and its handling\n   code since it's no longer needed\n\nThis ensures WBT is properly initialized before any IO can be submitted,\npreventing the counter from going negative."
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "block/bfq-iosched.c",
                        "block/blk-sysfs.c",
                        "block/blk-wbt.c",
                        "block/blk-wbt.h",
                        "block/elevator.c",
                        "block/elevator.h"
                    ],
                    "versions": [
                        {
                            "version": "78c271344b6f64ce24c845e54903e09928cf2061",
                            "lessThan": "f55201fb3becff6a903fd29f4d1147cc7e91eb0c",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "78c271344b6f64ce24c845e54903e09928cf2061",
                            "lessThan": "9869d3a6fed381f3b98404e26e1afc75d680cbf9",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                },
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "block/bfq-iosched.c",
                        "block/blk-sysfs.c",
                        "block/blk-wbt.c",
                        "block/blk-wbt.h",
                        "block/elevator.c",
                        "block/elevator.h"
                    ],
                    "versions": [
                        {
                            "version": "6.16",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.16",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.3",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.19",
                            "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": "6.16",
                                    "versionEndExcluding": "6.18.3"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.16",
                                    "versionEndExcluding": "6.19"
                                }
                            ]
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/f55201fb3becff6a903fd29f4d1147cc7e91eb0c"
                },
                {
                    "url": "https://git.kernel.org/stable/c/9869d3a6fed381f3b98404e26e1afc75d680cbf9"
                }
            ],
            "title": "block: fix race between wbt_enable_default and IO submission",
            "x_generator": {
                "engine": "bippy-1.2.0"
            }
        }
    }
}