CVE-2026-64112 (GCVE-0-2026-64112)
Vulnerability from cvelistv5
Published
2026-07-19 15:40
Modified
2026-08-05 12:39
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: rbd: eliminate a race in lock_dwork draining on unmap Given how rbd_lock_add_request() and rbd_img_exclusive_lock() are written, lock_dwork may be (re)queued more than it's actually needed: for example in case a new I/O request comes in while we are in the middle of rbd_acquire_lock() on behalf of another I/O request. This is expected and with rbd_release_lock() preemptively canceling lock_dwork is benign under normal operation. A more problematic example is maybe_kick_acquire(): if (have_requests || delayed_work_pending(&rbd_dev->lock_dwork)) { dout("%s rbd_dev %p kicking lock_dwork\n", __func__, rbd_dev); mod_delayed_work(rbd_dev->task_wq, &rbd_dev->lock_dwork, 0); } It's not unrealistic for lock_dwork to get canceled right after delayed_work_pending() returns true and for mod_delayed_work() to requeue it right there anyway. This is a classic TOCTOU race. When it comes to unmapping the image, there is an implicit assumption of no self-initiated exclusive lock activity past the point of return from rbd_dev_image_unlock() which unlocks the lock if it happens to be held. This unlock is assumed to be final and lock_dwork (as well as all other exclusive lock tasks, really) isn't expected to get queued again. However, lock_dwork is canceled only in cancel_tasks_sync() (i.e. later in the unmap sequence) and on top of that the cancellation can get in effect nullified by maybe_kick_acquire(). This may result in rbd_acquire_lock() executing after rbd_dev_device_release() and rbd_dev_image_release() run and free and/or reset a bunch of things. One of the possible failure modes then is a violated rbd_assert(rbd_image_format_valid(rbd_dev->image_format)); in rbd_dev_header_info() which is called via rbd_dev_refresh() from rbd_post_acquire_action(). Redo exclusive lock task draining to provide saner semantics and try to meet the assumptions around rbd_dev_image_unlock().
References
Impacted products
Vendor Product Version
Linux Linux Version: fd22aef8b47cfc068448df65c1183698b0abd815
Version: fd22aef8b47cfc068448df65c1183698b0abd815
Version: fd22aef8b47cfc068448df65c1183698b0abd815
Version: fd22aef8b47cfc068448df65c1183698b0abd815
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/rbd.c"
          ],
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        {
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          "programFiles": [
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          ],
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          "vendor": "Linux",
          "versions": [
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              "version": "4.12"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.92",
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            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.34",
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            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.92",
                  "versionStartIncluding": "4.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.34",
                  "versionStartIncluding": "4.12",
                  "vulnerable": true
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                {
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
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                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrbd: eliminate a race in lock_dwork draining on unmap\n\nGiven how rbd_lock_add_request() and rbd_img_exclusive_lock() are\nwritten, lock_dwork may be (re)queued more than it\u0027s actually needed:\nfor example in case a new I/O request comes in while we are in the\nmiddle of rbd_acquire_lock() on behalf of another I/O request.  This is\nexpected and with rbd_release_lock() preemptively canceling lock_dwork\nis benign under normal operation.\n\nA more problematic example is maybe_kick_acquire():\n\n    if (have_requests || delayed_work_pending(\u0026rbd_dev-\u003elock_dwork)) {\n            dout(\"%s rbd_dev %p kicking lock_dwork\\n\", __func__, rbd_dev);\n            mod_delayed_work(rbd_dev-\u003etask_wq, \u0026rbd_dev-\u003elock_dwork, 0);\n    }\n\nIt\u0027s not unrealistic for lock_dwork to get canceled right after\ndelayed_work_pending() returns true and for mod_delayed_work() to\nrequeue it right there anyway.  This is a classic TOCTOU race.\n\nWhen it comes to unmapping the image, there is an implicit assumption\nof no self-initiated exclusive lock activity past the point of return\nfrom rbd_dev_image_unlock() which unlocks the lock if it happens to be\nheld.  This unlock is assumed to be final and lock_dwork (as well as\nall other exclusive lock tasks, really) isn\u0027t expected to get queued\nagain.  However, lock_dwork is canceled only in cancel_tasks_sync()\n(i.e. later in the unmap sequence) and on top of that the cancellation\ncan get in effect nullified by maybe_kick_acquire().  This may result\nin rbd_acquire_lock() executing after rbd_dev_device_release() and\nrbd_dev_image_release() run and free and/or reset a bunch of things.\nOne of the possible failure modes then is a violated\n\n    rbd_assert(rbd_image_format_valid(rbd_dev-\u003eimage_format));\n\nin rbd_dev_header_info() which is called via rbd_dev_refresh() from\nrbd_post_acquire_action().\n\nRedo exclusive lock task draining to provide saner semantics and try\nto meet the assumptions around rbd_dev_image_unlock()."
        }
      ],
      "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 - Exploitation requires writing to /sys/bus/rbd/remove (or the equivalent error-path teardown during map), which is a local sysfs syscall path; network-delivered Ceph lock notifications can assist the race but cannot complete exploitation without this local unmap action.\nAC:L - The attacker controls both sides of the TOCTOU race by concurrently unmapping the device (sysfs remove) while driving lock activity through block I/O or lock-notification handling, making the race winnable with repeated attempts.\nPR:L - Both map and unmap operations require CAP_SYS_ADMIN, which is obtainable by an unprivileged user via user namespaces (unshare -Urn); per kernel CNA guidance this is PR:L rather than PR:H.\nUI:N - No victim interaction is required; the attacker can trigger the race programmatically through concurrent sysfs unmap and I/O or lock-notification activity.\nS:U - Impact is confined to kernel memory corruption and crash on the host running the RBD client; it does not cross a VM, container, or IOMMU security boundary.\nC:H - The bug allows rbd_acquire_lock() to operate on an rbd_device after rbd_dev_image_release() has freed and reset fields, constituting a use-after-free that can expose or dereference freed kernel heap data.\nI:H - Use-after-free on rbd_device and associated header structures provides memory corruption primitives that could be leveraged for arbitrary kernel writes or control-flow hijacking, not merely a clean crash.\nA:H - A confirmed failure mode is rbd_assert() triggering BUG() (kernel panic), and the underlying UAF can also cause oops or hang during post-teardown lock acquisition."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:39:21.112Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3427d7ae38337066ce88b68302e285d344ab756b"
        },
        {
          "url": "https://git.kernel.org/stable/c/9dcd4f5c99b491c37be90b0bd9988db48225fb75"
        },
        {
          "url": "https://git.kernel.org/stable/c/9400efc76b42c751211974a25c91d2c19c65b01b"
        },
        {
          "url": "https://git.kernel.org/stable/c/9fc75b71fdd38465c76c6f6a884cdd4ae3c72d90"
        }
      ],
      "title": "rbd: eliminate a race in lock_dwork draining on unmap",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64112",
    "datePublished": "2026-07-19T15:40:13.652Z",
    "dateReserved": "2026-07-19T07:54:57.035Z",
    "dateUpdated": "2026-08-05T12:39:21.112Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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