{"id":"CVE-2025-38689","summary":"x86/fpu: Fix NULL dereference in avx512_status()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/fpu: Fix NULL dereference in avx512_status()\n\nProblem\n-------\nWith CONFIG_X86_DEBUG_FPU enabled, reading /proc/[kthread]/arch_status\ncauses a warning and a NULL pointer dereference.\n\nThis is because the AVX-512 timestamp code uses x86_task_fpu() but\ndoesn't check it for NULL. CONFIG_X86_DEBUG_FPU addles that function\nfor kernel threads (PF_KTHREAD specifically), making it return NULL.\n\nThe point of the warning was to ensure that kernel threads only access\ntask-\u003efpu after going through kernel_fpu_begin()/_end(). Note: all\nkernel tasks exposed in /proc have a valid task-\u003efpu.\n\nSolution\n--------\nOne option is to silence the warning and check for NULL from\nx86_task_fpu(). However, that warning is fairly fresh and seems like a\ndefense against misuse of the FPU state in kernel threads.\n\nInstead, stop outputting AVX-512_elapsed_ms for kernel threads\naltogether. The data was garbage anyway because avx512_timestamp is\nonly updated for user threads, not kernel threads.\n\nIf anyone ever wants to track kernel thread AVX-512 use, they can come\nback later and do it properly, separate from this bug fix.\n\n[ dhansen: mostly rewrite changelog ]","modified":"2026-04-02T12:48:05.222841Z","published":"2025-09-04T15:32:43.530Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38689.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2ca887e81095b99d890a8878841f36f4920181e6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/31cd31c9e17ece125aad27259501a2af69ccb020"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38689.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-38689"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"22aafe3bcb67472effdea1ccf0df20280192bbaf"},{"fixed":"2ca887e81095b99d890a8878841f36f4920181e6"},{"fixed":"31cd31c9e17ece125aad27259501a2af69ccb020"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-38689.json"}}],"schema_version":"1.7.5"}