CVE-2026-93266: arm64: RSI: fix field-spanning write warning in attestation token init
In the Linux kernel, the following vulnerability has been resolved:
arm64: RSI: fix field-spanning write warning in attestation token init
The challenge is passed in registers a1 through a8. However, copying to ®s.a1 makes FORTIFY treat the destination as the single a1 field, resulting in a field-spanning write warning. [1]
Overlay the SMCCC register structure with an RSI-specific argument layout and copy the challenge into an explicit 64-byte array. This keeps the existing a1-a8 argument encoding while giving the copy a correctly sized destination object.
[1] memcpy: detected field-spanning write (size 64) of single field "®s.a1" at ./arch/arm64/include/asm/rsicmds.h:119 (size 8) WARNING: ./arch/arm64/include/asm/rsicmds.h:119 at rsiattestationtokeninit+0xdc/0xf8 [armccaguest], CPU#0: cat/3314
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
Upgrade
ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1
Event History
Frequently Asked Questions
Which systems are implicated by the reported warning?
The warning is reported in the arm64 RSI attestation-token initialization path, with the trace identifying the arm_cca_guest component. The affected operation passes a 64-byte challenge through SMCCC registers a1 through a8.
How can I identify this condition in logs?
FORTIFY reports a field-spanning write of size 64 to the single field ®s.a1, whose field size is 8 bytes. The warning identifies rsi_attestation_token_init and arch/arm64/include/asm/rsi_cmds.h:119.
Does the correction change the register argument encoding?
No. The correction overlays the SMCCC register structure with an RSI-specific argument layout and copies the challenge into an explicit 64-byte array while retaining the existing a1-a8 encoding.