The patch titled
Subject: mm,page_owner: defer enablement of static branch
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mmpage_owner-defer-enablement-of-static-branch.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mmpage_owner-defer-enablement-of-static-branch.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Oscar Salvador <osalvador@xxxxxxx>
Subject: mm,page_owner: defer enablement of static branch
Date: Tue, 9 Apr 2024 15:17:15 +0200
Kefeng Wang reported that he was seeing some memory leaks with kmemleak
with page_owner enabled.
The reason is that we enable the page_owner_inited static branch and then
proceed with the linking of stack_list struct to dummy_stack, which means
that exists a race window between these two steps where we can have pages
already being allocated calling add_stack_record_to_list(), allocating
objects and linking them to stack_list, but then we set stack_list
pointing to dummy_stack in init_page_owner. Which means that the objects
that have been allocated during that time window are unreferenced and
lost.
Fix this by deferring the enablement of the branch until we have properly
set up the list.
Link: https://lkml.kernel.org/r/20240409131715.13632-1-osalvador@xxxxxxx
Fixes: 4bedfb314bdd ("mm,page_owner: maintain own list of stack_records structs")
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Reported-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-mm/74b147b0-718d-4d50-be75-d6afc801cd24@xxxxxxxxxx/
Tested-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_owner.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/page_owner.c~mmpage_owner-defer-enablement-of-static-branch
+++ a/mm/page_owner.c
@@ -118,7 +118,6 @@ static __init void init_page_owner(void)
register_dummy_stack();
register_failure_stack();
register_early_stack();
- static_branch_enable(&page_owner_inited);
init_early_allocated_pages();
/* Initialize dummy and failure stacks and link them to stack_list */
dummy_stack.stack_record = __stack_depot_get_stack_record(dummy_handle);
@@ -129,6 +128,7 @@ static __init void init_page_owner(void)
refcount_set(&failure_stack.stack_record->count, 1);
dummy_stack.next = &failure_stack;
stack_list = &dummy_stack;
+ static_branch_enable(&page_owner_inited);
}
struct page_ext_operations page_owner_ops = {
_
Patches currently in -mm which might be from osalvador@xxxxxxx are
mmpage_owner-update-metadata-for-tail-pages.patch
mmpage_owner-fix-refcount-imbalance.patch
mmpage_owner-fix-accounting-of-pages-when-migrating.patch
mmpage_owner-fix-printing-of-stack-records.patch
mmswapops-update-check-in-is_pfn_swap_entry-for-hwpoison-entries.patch
mmpage_owner-defer-enablement-of-static-branch.patch
