In the Linux kernel, the following vulnerability has been resolved:
ufs: validate cylinder group metadata before caching it
ufs_read_cylinder() copies the cylinder group index and the rotor
positions straight from the on-disk group and caches them without any
check:
ucpi->c_cgx = fs32_to_cpu(sb, ucg->cg_cgx);
ucpi->c_rotor = fs32_to_cpu(sb, ucg->cg_rotor);
ucpi->c_frotor = fs32_to_cpu(sb, ucg->cg_frotor);
ucpi->c_irotor = fs32_to_cpu(sb, ucg->cg_irotor);
They are then used as indices during allocation and free:
- c_cgx indexes the cylinder summary array as
UFS_SB(sb)->fs_cs(ucpi->c_cgx), so a value past s_ncg writes a 32
bit count outside the s_csp allocation.
- c_frotor becomes a bitmap scan start, start = c_frotor >> 3, and
then length = ((s_fpg + 7) >> 3) - start. A start beyond the block
bitmap wraps the unsigned length to a huge value, so ubh_scanc()
walks far past the cylinder group buffers. c_irotor drives the
inode bitmap the same way.
A crafted image can set any of these freely, turning an ordinary
allocation into an out of bounds access.
Reject a cylinder group whose recorded index does not match the group
being read, or whose rotors fall outside the group, before the metadata
is cached. Valid filesystems keep cg_cgx equal to the group number and
the rotors within the group, so only malformed images are rejected.
ufs: validate cylinder group metadata before caching it
ufs_read_cylinder() copies the cylinder group index and the rotor
positions straight from the on-disk group and caches them without any
check:
ucpi->c_cgx = fs32_to_cpu(sb, ucg->cg_cgx);
ucpi->c_rotor = fs32_to_cpu(sb, ucg->cg_rotor);
ucpi->c_frotor = fs32_to_cpu(sb, ucg->cg_frotor);
ucpi->c_irotor = fs32_to_cpu(sb, ucg->cg_irotor);
They are then used as indices during allocation and free:
- c_cgx indexes the cylinder summary array as
UFS_SB(sb)->fs_cs(ucpi->c_cgx), so a value past s_ncg writes a 32
bit count outside the s_csp allocation.
- c_frotor becomes a bitmap scan start, start = c_frotor >> 3, and
then length = ((s_fpg + 7) >> 3) - start. A start beyond the block
bitmap wraps the unsigned length to a huge value, so ubh_scanc()
walks far past the cylinder group buffers. c_irotor drives the
inode bitmap the same way.
A crafted image can set any of these freely, turning an ordinary
allocation into an out of bounds access.
Reject a cylinder group whose recorded index does not match the group
being read, or whose rotors fall outside the group, before the metadata
is cached. Valid filesystems keep cg_cgx equal to the group number and
the rotors within the group, so only malformed images are rejected.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Fri, 25 Sep 2026 10:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: ufs: validate cylinder group metadata before caching it ufs_read_cylinder() copies the cylinder group index and the rotor positions straight from the on-disk group and caches them without any check: ucpi->c_cgx = fs32_to_cpu(sb, ucg->cg_cgx); ucpi->c_rotor = fs32_to_cpu(sb, ucg->cg_rotor); ucpi->c_frotor = fs32_to_cpu(sb, ucg->cg_frotor); ucpi->c_irotor = fs32_to_cpu(sb, ucg->cg_irotor); They are then used as indices during allocation and free: - c_cgx indexes the cylinder summary array as UFS_SB(sb)->fs_cs(ucpi->c_cgx), so a value past s_ncg writes a 32 bit count outside the s_csp allocation. - c_frotor becomes a bitmap scan start, start = c_frotor >> 3, and then length = ((s_fpg + 7) >> 3) - start. A start beyond the block bitmap wraps the unsigned length to a huge value, so ubh_scanc() walks far past the cylinder group buffers. c_irotor drives the inode bitmap the same way. A crafted image can set any of these freely, turning an ordinary allocation into an out of bounds access. Reject a cylinder group whose recorded index does not match the group being read, or whose rotors fall outside the group, before the metadata is cached. Valid filesystems keep cg_cgx equal to the group number and the rotors within the group, so only malformed images are rejected. | |
| Title | ufs: validate cylinder group metadata before caching it | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:22:44.197Z
Reserved: 2026-09-25T10:18:58.203Z
Link: CVE-2026-97926
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:19.833
Modified: 2026-09-25T11:17:19.833
Link: CVE-2026-97926
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.