{"id":"AZL-53643","summary":"CVE-2024-50275 affecting package kernel for versions less than 5.15.176.3-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\narm64/sve: Discard stale CPU state when handling SVE traps\n\nThe logic for handling SVE traps manipulates saved FPSIMD/SVE state\nincorrectly, and a race with preemption can result in a task having\nTIF_SVE set and TIF_FOREIGN_FPSTATE clear even though the live CPU state\nis stale (e.g. with SVE traps enabled). This has been observed to result\nin warnings from do_sve_acc() where SVE traps are not expected while\nTIF_SVE is set:\n\n|         if (test_and_set_thread_flag(TIF_SVE))\n|                 WARN_ON(1); /* SVE access shouldn't have trapped */\n\nWarnings of this form have been reported intermittently, e.g.\n\n  https://lore.kernel.org/linux-arm-kernel/CA+G9fYtEGe_DhY2Ms7+L7NKsLYUomGsgqpdBj+QwDLeSg=JhGg@mail.gmail.com/\n  https://lore.kernel.org/linux-arm-kernel/000000000000511e9a060ce5a45c@google.com/\n\nThe race can occur when the SVE trap handler is preempted before and\nafter manipulating the saved FPSIMD/SVE state, starting and ending on\nthe same CPU, e.g.\n\n| void do_sve_acc(unsigned long esr, struct pt_regs *regs)\n| {\n|         // Trap on CPU 0 with TIF_SVE clear, SVE traps enabled\n|         // task-\u003efpsimd_cpu is 0.\n|         // per_cpu_ptr(&fpsimd_last_state, 0) is task.\n|\n|         ...\n|\n|         // Preempted; migrated from CPU 0 to CPU 1.\n|         // TIF_FOREIGN_FPSTATE is set.\n|\n|         get_cpu_fpsimd_context();\n|\n|         if (test_and_set_thread_flag(TIF_SVE))\n|                 WARN_ON(1); /* SVE access shouldn't have trapped */\n|\n|         sve_init_regs() {\n|                 if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {\n|                         ...\n|                 } else {\n|                         fpsimd_to_sve(current);\n|                         current-\u003ethread.fp_type = FP_STATE_SVE;\n|                 }\n|         }\n|\n|         put_cpu_fpsimd_context();\n|\n|         // Preempted; migrated from CPU 1 to CPU 0.\n|         // task-\u003efpsimd_cpu is still 0\n|         // If per_cpu_ptr(&fpsimd_last_state, 0) is still task then:\n|         // - Stale HW state is reused (with SVE traps enabled)\n|         // - TIF_FOREIGN_FPSTATE is cleared\n|         // - A return to userspace skips HW state restore\n| }\n\nFix the case where the state is not live and TIF_FOREIGN_FPSTATE is set\nby calling fpsimd_flush_task_state() to detach from the saved CPU\nstate. This ensures that a subsequent context switch will not reuse the\nstale CPU state, and will instead set TIF_FOREIGN_FPSTATE, forcing the\nnew state to be reloaded from memory prior to a return to userspace.","modified":"2026-04-01T05:16:35.347693Z","published":"2024-11-19T02:16:29Z","upstream":["CVE-2024-50275"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-50275"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:2","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.15.176.3-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-53643.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}