On 4/9/24 3:17 PM, Oscar Salvador wrote: > Kefeng Wang reported that he was seeing some memory leaks with kmemleak > with page_owner enabled. > The reason behind 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. > > 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> > Fixes: 4bedfb314bdd ("mm,page_owner: maintain own list of stack_records structs") That's in rc1 so ideally mm-hotfixes. > Signed-off-by: Oscar Salvador <osalvador@xxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > --- > Special thanks and kudos go to Kefeng Wang for helping me out chasing > down this bug, as I could not reproduce it with any of my machines, and > to Vlastimil to bring another pair of eyes, which was very helpful. > > mm/page_owner.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 9bef0b442863..742f432e5bf0 100644 > --- a/mm/page_owner.c > +++ b/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 = {
