arm64/sve: Discard stale CPU state when handling SVE traps

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Summary

CVECVE-2024-50275
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-11-19 02:16:29 UTC
Updated2026-08-04 11:21:39 UTC
DescriptionIn 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/[email protected]/ 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.

Risk And Classification

Primary CVSS: v3.1 7 HIGH from [email protected]

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem Types: NVD-CWE-noinfo

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7HIGHCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
3.1CNADECLARED7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected cccb78ce89c45a4414db712be4986edfb92434bd 51d3d80a6dc314982a9a0aeb0961085922a1aa15 git Not specified
CNA Linux Linux affected cccb78ce89c45a4414db712be4986edfb92434bd de529504b3274d57caf8f66800b714b0d3ee235a git Not specified
CNA Linux Linux affected cccb78ce89c45a4414db712be4986edfb92434bd 51d11ea0250d6ee461987403bbfd4b2abb5613a7 git Not specified
CNA Linux Linux affected cccb78ce89c45a4414db712be4986edfb92434bd fa9ce027b3ce37a2bb173bf2553b5caa438fd8c9 git Not specified
CNA Linux Linux affected cccb78ce89c45a4414db712be4986edfb92434bd 751ecf6afd6568adc98f2a6052315552c0483d18 git Not specified
CNA Linux Linux affected 5.13 Not specified
CNA Linux Linux unaffected 5.13 semver Not specified
CNA Linux Linux unaffected 5.15.174 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.120 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.61 6.6.* semver Not specified
CNA Linux Linux unaffected 6.11.8 6.11.* semver Not specified
CNA Linux Linux unaffected 6.12 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/51d3d80a6dc314982a9a0aeb0961085922a1aa15 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/de529504b3274d57caf8f66800b714b0d3ee235a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/51d11ea0250d6ee461987403bbfd4b2abb5613a7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/03/msg00001.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/751ecf6afd6568adc98f2a6052315552c0483d18 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/fa9ce027b3ce37a2bb173bf2553b5caa438fd8c9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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