{"id":"CVE-2026-93253","title":"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 …","summary":"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 …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 27c3a5967f054ab666704cb28f2aeb18ca07cab7 < 811fdac2d1bdf0b0d3fda262aac288ddd13a1422","Linux >= 27c3a5967f054ab666704cb28f2aeb18ca07cab7 < 2b58c749b8c5244e259a0230bc57b10b010dc545","Linux 7.0"],"published":"2026-09-24","updated":"2026-09-24","sourceUpdated":"2026-09-24T16:17:21.640","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-93253","references":[{"url":"https://git.kernel.org/stable/c/2b58c749b8c5244e259a0230bc57b10b010dc545","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/811fdac2d1bdf0b0d3fda262aac288ddd13a1422","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-24T16:47:15.832Z","slug":"CVE-2026-93253","body":"## Overview\n\nIn 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   <TASK>\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   </TASK>\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/\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}