CVE-2024-50275
Dec. 14, 2024, 9:15 p.m.
Tags
CVSS Score
Products Impacted
Vendor | Product | Versions |
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linux |
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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.
Weaknesses
Date
Published: Nov. 19, 2024, 2:16 a.m.
Last Modified: Dec. 14, 2024, 9:15 p.m.
Status : Modified
CVE has been recently published to the CVE List and has been received by the NVD.
More infoSource
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CPEs
Type | Vendor | Product | Version | Update | Edition | Language | Software Edition | Target Software | Target Hardware | Other Information |
---|---|---|---|---|---|---|---|---|---|---|
o | linux | linux_kernel | / | / | / | / | / | / | / | / |
o | linux | linux_kernel | / | / | / | / | / | / | / | / |
o | linux | linux_kernel | 6.12 | rc1 | / | / | / | / | / | / |
o | linux | linux_kernel | 6.12 | rc2 | / | / | / | / | / | / |
o | linux | linux_kernel | 6.12 | rc3 | / | / | / | / | / | / |
o | linux | linux_kernel | 6.12 | rc4 | / | / | / | / | / | / |
o | linux | linux_kernel | 6.12 | rc5 | / | / | / | / | / | / |
o | linux | linux_kernel | 6.12 | rc6 | / | / | / | / | / | / |
CVSS Data
Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
LOW
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Base Score
Exploitability Score
Impact Score
Base Severity
HIGHCVSS Vector String
The CVSS vector string provides an in-depth view of the vulnerability metrics.
View Vector StringCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H