CVE-2026-90195
riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args
Description
In the Linux kernel, the following vulnerability has been resolved: riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args On RV64, the ABI requires sign-extension for signed 1-byte and 2-byte kfunc args. However, the RV64 JIT currently does not perform sign-extension for such kfunc args. Before commit 7ce090afbf72 ("bpf: Infer zext_dst based on static register liveness analysis"), state pruning could potentially omit zero-extension of 32-bit subregisters, which inadvertently masked the above issue by making the args appear as if they had been properly sign-extended. After that commit, the problem is exposed, causing the kfunc_call/kfunc_call_test4 selftest to fail. Fix this by extending the existing sign-extension logic to handle signed 1-byte and 2-byte kfunc args as well.
INFO
Published Date :
Sept. 17, 2026, 5:17 p.m.
Last Modified :
Sept. 17, 2026, 5:17 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Update the Linux kernel to the latest version.
- Apply the provided security patch.
- Verify kfunc argument handling.
References to Advisories, Solutions, and Tools
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CVE-2026-90195.
CWE - Common Weakness Enumeration
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associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
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stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-90195
weaknesses.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 17, 2026
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args On RV64, the ABI requires sign-extension for signed 1-byte and 2-byte kfunc args. However, the RV64 JIT currently does not perform sign-extension for such kfunc args. Before commit 7ce090afbf72 ("bpf: Infer zext_dst based on static register liveness analysis"), state pruning could potentially omit zero-extension of 32-bit subregisters, which inadvertently masked the above issue by making the args appear as if they had been properly sign-extended. After that commit, the problem is exposed, causing the kfunc_call/kfunc_call_test4 selftest to fail. Fix this by extending the existing sign-extension logic to handle signed 1-byte and 2-byte kfunc args as well. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/90xxx/CVE-2026-90195.json">CVE-2026-90195</a> Added Reference https://git.kernel.org/stable/c/555fc6f1caf00ce7005e732b688da26c0dc3c5c5 Added Reference https://git.kernel.org/stable/c/71dbd143be598954ae103feadd12692aeb0f2f88 Added Reference https://git.kernel.org/stable/c/801ae90f8ce099187e6224cec7d72d07a4df0324 Added Reference https://git.kernel.org/stable/c/f2aaa621591093cfe8224a25ef2f04a3b1e304b0