From: Muchun Song <songmuchun@bytedance.com>
Date: Tue, 31 Mar 2026 11:37:24 +0000 (+0800)
Subject: mm/sparse: fix preinited section_mem_map clobbering on failure path
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7cf6d940f4032d87d9cfe6b27c0e49e309818e5d;p=thirdparty%2Fkernel%2Flinux.git

mm/sparse: fix preinited section_mem_map clobbering on failure path

sparse_init_nid() is careful to leave alone every section whose vmemmap
has already been set up by sparse_vmemmap_init_nid_early(); it only clears
section_mem_map for the rest:

        if (!preinited_vmemmap_section(ms))
                ms->section_mem_map = 0;

A leftover line after that conditional block

        ms->section_mem_map = 0;

was supposed to be deleted but was missed in the failure path, causing the
field to be overwritten for all sections when memory allocation fails,
effectively destroying the pre-initialization check.

Drop the stray assignment so that preinited sections retain their
already valid state.

Those pre-inited sections (HugeTLB pages) are not activated.  However,
such failures are extremely rare, so I don't see any major userspace
issues.

Link: https://lore.kernel.org/20260331113724.2080833-1-songmuchun@bytedance.com
Fixes: d65917c42373 ("mm/sparse: allow for alternate vmemmap section init at boot")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed by: Donet Tom <donettom@linux.ibm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/sparse.c b/mm/sparse.c
index 007fd52c621e..effdac6b0ab1 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -403,7 +403,6 @@ failed:
 		ms = __nr_to_section(pnum);
 		if (!preinited_vmemmap_section(ms))
 			ms->section_mem_map = 0;
-		ms->section_mem_map = 0;
 	}
 }