{"api_version":"1","generated_at":"2026-10-05T17:17:07+00:00","cve":"CVE-2026-97902","urls":{"html":"https://cve.report/CVE-2026-97902","api":"https://cve.report/api/cve/CVE-2026-97902.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-97902","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-97902"},"summary":{"title":"fs: don't return -EINVAL for successful nested thaw","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs: don't 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's\nunlock_fs() ignores bdev_thaw()'s return value, so nothing rebalances\nthe count. After the user's FITHAW and umount, the block device can\nnever be mounted again:\n\n    dm-1: Can't 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 -> 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()'s documentation already describes the intended\nsemantics: \"If this function returns zero it doesn't 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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-25 11:17:17","updated_at":"2026-09-25 11:17:17"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/ff2a694f6613d54ebd77ba72583d4d94446f55bd","name":"https://git.kernel.org/stable/c/ff2a694f6613d54ebd77ba72583d4d94446f55bd","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/111339816138f042a59778322f941edc26903484","name":"https://git.kernel.org/stable/c/111339816138f042a59778322f941edc26903484","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/fe967191e5851ea79818c5fe4e781c3882139218","name":"https://git.kernel.org/stable/c/fe967191e5851ea79818c5fe4e781c3882139218","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/76e478499913dc1f368aebe85b28b7d1265985ff","name":"https://git.kernel.org/stable/c/76e478499913dc1f368aebe85b28b7d1265985ff","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-97902","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97902","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7366f8b6fc6aa21c4199cb5d337b023df69745b0 111339816138f042a59778322f941edc26903484 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7366f8b6fc6aa21c4199cb5d337b023df69745b0 76e478499913dc1f368aebe85b28b7d1265985ff git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7366f8b6fc6aa21c4199cb5d337b023df69745b0 ff2a694f6613d54ebd77ba72583d4d94446f55bd git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7366f8b6fc6aa21c4199cb5d337b023df69745b0 fe967191e5851ea79818c5fe4e781c3882139218 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.8","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.8 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.111 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.53 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.7 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"97902","cve":"CVE-2026-97902","epss":"0.002000000","percentile":"0.088160000","score_date":"2026-09-27","updated_at":"2026-09-28 00:02:24"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"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"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.111","versionStartIncluding":"6.8","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.53","versionStartIncluding":"6.8","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.7","versionStartIncluding":"6.8","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc3","versionStartIncluding":"6.8","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs: don't 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's\nunlock_fs() ignores bdev_thaw()'s return value, so nothing rebalances\nthe count. After the user's FITHAW and umount, the block device can\nnever be mounted again:\n\n    dm-1: Can't 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 -> 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()'s documentation already describes the intended\nsemantics: \"If this function returns zero it doesn't 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."}],"providerMetadata":{"dateUpdated":"2026-09-25T10:22:29.259Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/111339816138f042a59778322f941edc26903484"},{"url":"https://git.kernel.org/stable/c/76e478499913dc1f368aebe85b28b7d1265985ff"},{"url":"https://git.kernel.org/stable/c/ff2a694f6613d54ebd77ba72583d4d94446f55bd"},{"url":"https://git.kernel.org/stable/c/fe967191e5851ea79818c5fe4e781c3882139218"}],"title":"fs: don't return -EINVAL for successful nested thaw","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-97902","datePublished":"2026-09-25T10:22:29.259Z","dateReserved":"2026-09-25T10:18:58.200Z","dateUpdated":"2026-09-25T10:22:29.259Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-25 11:17:17","lastModifiedDate":"2026-09-25 11:17:17","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"97902","Ordinal":"1","Title":"fs: don't return -EINVAL for successful nested thaw","CVE":"CVE-2026-97902","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"97902","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs: don't 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's\nunlock_fs() ignores bdev_thaw()'s return value, so nothing rebalances\nthe count. After the user's FITHAW and umount, the block device can\nnever be mounted again:\n\n    dm-1: Can't 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 -> 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()'s documentation already describes the intended\nsemantics: \"If this function returns zero it doesn't 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.","Type":"Description","Title":"fs: don't return -EINVAL for successful nested thaw"}]}}}