FKIE_CVE-2026-97902

Vulnerability from fkie_nvd - Published: 2026-09-25 11:17 - Updated: 2026-09-25 11:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: fs: don't return -EINVAL for successful nested thaw Commit 7366f8b6fc6a ("fs: handle freezing from multiple devices") replaced the freeze_holders bitmask with per-holder counters to allow nested freezes. In the bitmask version, a thaw that released a shared hold while another holder remained returned 0. Since the rework, thaw_super_locked() drops the freeze reference via freeze_dec() but then returns -EINVAL when other freezers remain, misinforming the caller: the thaw did succeed, the superblock just stays frozen for the remaining holders. This breaks bdev-initiated freezing. When a filesystem is frozen with FIFREEZE and additionally frozen via bdev_freeze() -- which nests by design, see fs_bdev_freeze() -- the subsequent bdev_thaw() receives -EINVAL from the holder op although its freeze reference was dropped, and therefore keeps bd_fsfreeze_count elevated. Then device-mapper's unlock_fs() ignores bdev_thaw()'s return value, so nothing rebalances the count. After the user's FITHAW and umount, the block device can never be mounted again: dm-1: Can't mount, blockdev is frozen There is no way for userspace to drop the leaked count; only destroying the block device (or a reboot) recovers the device. Reproducer (any kernel since v6.8): dmsetup create dut --table "0 $(blockdev --getsz "$DEV") linear $DEV 0" mkfs.ext4 /dev/mapper/dut mount /dev/mapper/dut /mnt fsfreeze --freeze /mnt # freeze_ucount == 1 dmsetup suspend dut # bd_fsfreeze_count == 1, ucount == 2 dmsetup resume dut # ucount 2 -> 1, but thaw_super() # returns -EINVAL, so bdev_thaw() # keeps bd_fsfreeze_count at 1 fsfreeze --unfreeze /mnt # filesystem thaws fine umount /mnt mount /dev/mapper/dut /mnt # EBUSY, forever The same happens with fsfreeze held across an LVM snapshot of the origin volume. fs_bdev_thaw()'s documentation already describes the intended semantics: "If this function returns zero it doesn't mean that the filesystem is unfrozen as it may have been frozen multiple times". Restore them by returning 0 when a nested thaw drops its hold while other freezers remain. Thawing without holding a freeze still fails with -EINVAL as may_unfreeze() rejects that case before the reference count is touched.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/111339816138f042a59778322f941edc26903484
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/76e478499913dc1f368aebe85b28b7d1265985ff
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fe967191e5851ea79818c5fe4e781c3882139218
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ff2a694f6613d54ebd77ba72583d4d94446f55bd
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/super.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "111339816138f042a59778322f941edc26903484",
              "status": "affected",
              "version": "7366f8b6fc6aa21c4199cb5d337b023df69745b0",
              "versionType": "git"
            },
            {
              "lessThan": "76e478499913dc1f368aebe85b28b7d1265985ff",
              "status": "affected",
              "version": "7366f8b6fc6aa21c4199cb5d337b023df69745b0",
              "versionType": "git"
            },
            {
              "lessThan": "ff2a694f6613d54ebd77ba72583d4d94446f55bd",
              "status": "affected",
              "version": "7366f8b6fc6aa21c4199cb5d337b023df69745b0",
              "versionType": "git"
            },
            {
              "lessThan": "fe967191e5851ea79818c5fe4e781c3882139218",
              "status": "affected",
              "version": "7366f8b6fc6aa21c4199cb5d337b023df69745b0",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/super.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs: don\u0027t return -EINVAL for successful nested thaw\n\nCommit 7366f8b6fc6a (\"fs: handle freezing from multiple devices\")\nreplaced the freeze_holders bitmask with per-holder counters to allow\nnested freezes. In the bitmask version, a thaw that released a shared\nhold while another holder remained returned 0. Since the rework,\nthaw_super_locked() drops the freeze reference via freeze_dec() but\nthen returns -EINVAL when other freezers remain, misinforming the\ncaller: the thaw did succeed, the superblock just stays frozen for the\nremaining holders.\n\nThis breaks bdev-initiated freezing. When a filesystem is frozen with\nFIFREEZE and additionally frozen via bdev_freeze() -- which nests by\ndesign, see fs_bdev_freeze() -- the subsequent bdev_thaw() receives\n-EINVAL from the holder op although its freeze reference was dropped,\nand therefore keeps bd_fsfreeze_count elevated. Then device-mapper\u0027s\nunlock_fs() ignores bdev_thaw()\u0027s return value, so nothing rebalances\nthe count. After the user\u0027s FITHAW and umount, the block device can\nnever be mounted again:\n\n    dm-1: Can\u0027t mount, blockdev is frozen\n\nThere is no way for userspace to drop the leaked count; only\ndestroying the block device (or a reboot) recovers the device.\n\nReproducer (any kernel since v6.8):\n\n    dmsetup create dut --table \"0 $(blockdev --getsz \"$DEV\") linear $DEV 0\"\n    mkfs.ext4 /dev/mapper/dut\n    mount /dev/mapper/dut /mnt\n    fsfreeze --freeze /mnt      # freeze_ucount == 1\n    dmsetup suspend dut         # bd_fsfreeze_count == 1, ucount == 2\n    dmsetup resume dut          # ucount 2 -\u003e 1, but thaw_super()\n                                # returns -EINVAL, so bdev_thaw()\n                                # keeps bd_fsfreeze_count at 1\n    fsfreeze --unfreeze /mnt    # filesystem thaws fine\n    umount /mnt\n    mount /dev/mapper/dut /mnt  # EBUSY, forever\n\nThe same happens with fsfreeze held across an LVM snapshot of the\norigin volume.\n\nfs_bdev_thaw()\u0027s documentation already describes the intended\nsemantics: \"If this function returns zero it doesn\u0027t mean that the\nfilesystem is unfrozen as it may have been frozen multiple times\".\nRestore them by returning 0 when a nested thaw drops its hold while\nother freezers remain. Thawing without holding a freeze still fails\nwith -EINVAL as may_unfreeze() rejects that case before the reference\ncount is touched."
    }
  ],
  "id": "CVE-2026-97902",
  "lastModified": "2026-09-25T11:17:17.000",
  "metrics": {},
  "published": "2026-09-25T11:17:17.000",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/111339816138f042a59778322f941edc26903484"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/76e478499913dc1f368aebe85b28b7d1265985ff"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/fe967191e5851ea79818c5fe4e781c3882139218"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ff2a694f6613d54ebd77ba72583d4d94446f55bd"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.