sparc: fix accurate exception reporting in copy_{from_to}_user for UltraSPARC III
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA.
Summary
In the Linux kernel, the following vulnerability has been resolved: sparc: fix accurate exception reporting in copy_{from_to}_user for UltraSPARC III Anthony Yznaga tracked down that a BUG_ON in ext4 code with large folios enabled resulted from copy_from_user() returning impossibly large values greater than the size to be copied. This lead to __copy_from_iter() returning impossible values instead of the actual number of bytes it was able to copy. The BUG_ON has been reported in https://lore.kernel.org/r/b14f55642207e63e907965e209f6323a0df6dcee.camel@physik.fu-berlin.de The referenced commit introduced exception handlers on user-space memory references in copy_from_user and copy_to_user. These handlers return from the respective function and calculate the remaining bytes left to copy using the current register contents. The exception handlers expect that %o2 has already been masked during the bulk copy loop, but the masking was performed after that loop. This will fix the return value of copy_from_user and copy_to_user in the faulting case. The behaviour of memcpy stays unchanged.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 4.5, 4.9
- Fix · CNA Linux (Linux) Fixed in 5.4.301, 5.10.246, 5.15.195, 6.1.156, 6.6.112, 6.12.53, 6.17.3, 6.18
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
Not affected: 5 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2025-40124
- 2026-10-03 Alias added: GHSA-v3c5-2xf8-7jwx
- 2026-11-07 Affected versions changed · Red Hat
References
Other 8
- https://git.kernel.org/stable/c/fdd43fe6d286f27b826572457a89c926f97e2d3a
- https://git.kernel.org/stable/c/1198077606aeffb102587c6ea079ce99641c99d4
- https://git.kernel.org/stable/c/1857cdca12c4aff58bf26a7005a4d02850c29927
- https://git.kernel.org/stable/c/91eda032eb16e5d2be27c95584665bc555bb5a90
- https://git.kernel.org/stable/c/dc766c4830a7e1e1ee9d7f77d4ab344f2eb23c8e
- https://git.kernel.org/stable/c/5ef9c94d7110e90260c06868cf1dcf899b9f25ee
- https://git.kernel.org/stable/c/e50377c6b3f278c9f3ef017ffce17f5fcc9dace4
- https://git.kernel.org/stable/c/47b49c06eb62504075f0f2e2227aee2e2c2a58b3
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Sources
- CVE-2025-40124 · CVE Program
- CVE-2025-40124 · NVD
- FIRST EPSS
- GHSA-v3c5-2xf8-7jwx · GitHub Advisory Database · CC BY 4.0
- CVE-2025-40124 · Red Hat security data · CC BY 4.0
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