From b3ef855262928c5e80e881895694891164c13fc8 Mon Sep 17 00:00:00 2001 From: Muchun Song Date: Fri, 12 Jun 2026 11:58:50 +0800 Subject: [PATCH] mm/sparse: panic on memmap and usemap allocation failure When vmemmap or usemap allocation fails, sparse_init_nid() currently marks the section non-present and continues. Later boot-time code can still walk PFNs in that section without checking for this partial setup, which leads to invalid accesses. subsection_map_init() can also touch an unallocated usemap. Auditing and fixing all early PFN walkers for this case is not worth the complexity. These allocation failures are expected to be fatal anyway, and other memory models already treat them that way. Make memmap and usemap allocation failures panic immediately instead of trying to recover and crashing later in less obvious ways. This is also consistent with how other memory model configurations handle memmap allocation failures. Link: https://lore.kernel.org/20260612035903.2468601-7-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Mike Rapoport (Microsoft) Acked-by: Oscar Salvador Cc: "Aneesh Kumar K.V" Cc: David Hildenbrand Cc: Frank van der Linden Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Oscar Salvador (SUSE) Cc: "Ritesh Harjani (IBM)" Cc: Usama Arif Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/sparse.c | 44 +++++++++----------------------------------- 1 file changed, 9 insertions(+), 35 deletions(-) diff --git a/mm/sparse.c b/mm/sparse.c index 16ac6df3c89f..c92bbc3f3aa3 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -239,15 +239,8 @@ struct page __init *__populate_section_memmap(unsigned long pfn, struct dev_pagemap *pgmap) { unsigned long size = section_map_size(); - struct page *map; - phys_addr_t addr = __pa(MAX_DMA_ADDRESS); - map = memmap_alloc(size, size, addr, nid, false); - if (!map) - panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%pa\n", - __func__, size, PAGE_SIZE, nid, &addr); - - return map; + return memmap_alloc(size, size, __pa(MAX_DMA_ADDRESS), nid, false); } #endif /* !CONFIG_SPARSEMEM_VMEMMAP */ @@ -300,17 +293,14 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, unsigned long map_count) { unsigned long pnum; - struct page *map; - struct mem_section *ms; - if (sparse_usage_init(nid, map_count)) { - pr_err("%s: node[%d] usemap allocation failed", __func__, nid); - goto failed; - } + if (sparse_usage_init(nid, map_count)) + panic("Failed to allocate usemap for node %d\n", nid); sparse_vmemmap_init_nid_early(nid); for_each_present_section_nr(pnum_begin, pnum) { + struct mem_section *ms; unsigned long pfn = section_nr_to_pfn(pnum); if (pnum >= pnum_end) @@ -318,34 +308,18 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, ms = __nr_to_section(pnum); if (!preinited_vmemmap_section(ms)) { + struct page *map; + map = __populate_section_memmap(pfn, PAGES_PER_SECTION, - nid, NULL, NULL); - if (!map) { - pr_err("%s: node[%d] memory map backing failed. Some memory will not be available.", - __func__, nid); - pnum_begin = pnum; - sparse_usage_fini(); - goto failed; - } + nid, NULL, NULL); + if (!map) + panic("Failed to allocate memmap for section %lu\n", pnum); memmap_boot_pages_add(DIV_ROUND_UP(PAGES_PER_SECTION * sizeof(struct page), PAGE_SIZE)); sparse_init_early_section(nid, map, pnum, 0); } } sparse_usage_fini(); - return; -failed: - /* - * We failed to allocate, mark all the following pnums as not present, - * except the ones already initialized earlier. - */ - for_each_present_section_nr(pnum_begin, pnum) { - if (pnum >= pnum_end) - break; - ms = __nr_to_section(pnum); - if (!preinited_vmemmap_section(ms)) - ms->section_mem_map = 0; - } } /*