{"id":"CVE-2026-93253","summary":"sched/isolation: Defer freeing of cpumask memblock memory to initcall","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched/isolation: Defer freeing of cpumask memblock memory to initcall\n\nWhen testing a linux-next kernel with commit 59bd1d914bb5 (\"memblock:\nwarn when freeing reserved memory before memory map is initialized\"),\nthe following warning was hit when there was a \"nohz_full\" kernel boot\nparameter.\n\n  Cannot free reserved memory because of deferred initialization of the memory map\n  WARNING: mm/memblock.c:904 at __free_reserved_area+0xde/0xf0, CPU#0: swapper/0/0\n    :\n  Call Trace:\n   \u003cTASK\u003e\n   memblock_phys_free+0xcb/0x100\n   housekeeping_init+0x14c/0x170\n   start_kernel+0x207/0x450\n   x86_64_start_reservations+0x24/0x30\n   x86_64_start_kernel+0xda/0xe0\n   common_startup_64+0x13e/0x141\n   \u003c/TASK\u003e\n\nIOW, we shouldn't free memblock allocated memory so early\nin the boot process when memory map isn't fully initialized in\ndeferred_init_memmap().\n\nFix it by saving the housekeeping cpumask memblock memory to be\nfreed into a llist free list in housekeeping_init() and add a new\nhousekeeping_late_init() helper to defer the actual freeing of memblock\nmemory to when initcall's are being processed. The cpumask memblock\nmemory is treated as a llist_node with the size of a \"long\" type which\nis also smallest cpumask size that can be allocated.\n\nThe non-atomic version of the llist APIs are used as there is no\ncontention.\n\nThis commit depends on the presence of commit 7c2eee9c1367 (\"memblock:\ndon't touch memblock arrays when memblock_free() is called late\")\nto prevent a KASAN UAF bug report [1].\n\n [1] https://lore.kernel.org/lkml/20260505051821.1107133-1-longman@redhat.com/","modified":"2026-09-25T03:48:53.943487991Z","published":"2026-09-24T15:51:29.259Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93253.json","cna_assigner":"Linux"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2b58c749b8c5244e259a0230bc57b10b010dc545"},{"type":"WEB","url":"https://git.kernel.org/stable/c/811fdac2d1bdf0b0d3fda262aac288ddd13a1422"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93253.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93253"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"27c3a5967f054ab666704cb28f2aeb18ca07cab7"},{"fixed":"811fdac2d1bdf0b0d3fda262aac288ddd13a1422"},{"fixed":"2b58c749b8c5244e259a0230bc57b10b010dc545"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93253.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.0.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93253.json"}}],"schema_version":"1.9.0"}