CVE-2025-40124
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.
- CVSS 3.1
- 7.8
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS
- 0.2% chance of exploitation in the next 30 days; higher than 5% of CVEs (scores of 2026-10-25)
- Published
- Modified
- Record from
- the NVD, synced
References
- https://git.kernel.org/stable/c/1198077606aeffb102587c6ea079ce99641c99d4
- https://git.kernel.org/stable/c/1857cdca12c4aff58bf26a7005a4d02850c29927
- https://git.kernel.org/stable/c/47b49c06eb62504075f0f2e2227aee2e2c2a58b3
- https://git.kernel.org/stable/c/5ef9c94d7110e90260c06868cf1dcf899b9f25ee
- https://git.kernel.org/stable/c/91eda032eb16e5d2be27c95584665bc555bb5a90