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CVE-2025-40126: sparc: fix accurate exception reporting in copy_{from_to}_user for UltraSPARC

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-11-12 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: sparc: fix accurate exception reporting in copy_{from_to}_user for UltraSPARC 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. This commit fixes a couple of bad calculations. This will fix the return value of copy_from_user and copy_to_user in the faulting case. The behaviour of memcpy stays unchanged.

Affected products

• Linux kernel: from 4.4.34 before 4.5; from 4.8.10 before 4.9; 4.9 — fixed in 4.5, 4.9, 6.18

How to fix

Upgrade to a fixed version: Linux kernel 4.5, 4.9, 6.18. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/0bf3dc3a2156f1c5ddaba4b85d09767874634114
• https://git.kernel.org/stable/c/41c18baee66134e6ef786eb075c1b6adb22432b0
• https://git.kernel.org/stable/c/4fba1713001195e59cfc001ff1f2837dab877efb
• https://git.kernel.org/stable/c/57c278500fce3cd4e1c540700c0b05426a958393
• https://git.kernel.org/stable/c/59424dc0d0e044b2eb007686a4724ddd91d57db5
• https://git.kernel.org/stable/c/674ff598148a28bae0b5372339de56f2abf0b1d1
• https://git.kernel.org/stable/c/7de3a75bbc8465d816336c74d50109e73501efab
• https://git.kernel.org/stable/c/9b137f277cc3297044aabd950f589e505d30104c

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