CVE-2026-97902
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.
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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:
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):
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.
Detalles técnicos trazas, registros y código del informe original
dm-1: Can't mount, blockdev is frozen
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, foreverCVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.20%
- Percentil entre todas las CVEs puntuadas: 9
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-97902",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7366f8b6fc6aa21c4199cb5d337b023df69745b0",
"lessThan": "111339816138f042a59778322f941edc26903484",
"versionType": "git"
},
{
"status": "affected",
"version": "7366f8b6fc6aa21c4199cb5d337b023df69745b0",
"lessThan": "76e478499913dc1f368aebe85b28b7d1265985ff",
"versionType": "git"
},
{
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"version": "7366f8b6fc6aa21c4199cb5d337b023df69745b0",
"lessThan": "ff2a694f6613d54ebd77ba72583d4d94446f55bd",
"versionType": "git"
},
{
"status": "affected",
"version": "7366f8b6fc6aa21c4199cb5d337b023df69745b0",
"lessThan": "fe967191e5851ea79818c5fe4e781c3882139218",
"versionType": "git"
}
],
"programFiles": [
"fs/super.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.8"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.8",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.111",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.53",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.7",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/super.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-25T11:17:17.000",
"references": [
{
"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",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"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."
}
],
"lastModified": "2026-09-25T11:17:17.000",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}