Although the retrieval of the stack_records for {dummy,failure}_handle
happen when page_owner gets initialized, there seems to be some situations
where stackdepot space has been already depleted by then, so we get
0-handles which make stack_records being NULL for those cases.
Be careful to 1) only bump stack_records refcount and 2) only access
stack_record fields if we actually have a non-null stack_record between
hands.
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202403051032.e2f865a-lkp@xxxxxxxxx
Fixes: 4bedfb314bdd ("mm,page_owner: implement the tracking of the stacks count")
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
---
mm/page_owner.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 033e349f6479..7163a1c44ccf 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -107,8 +107,10 @@ static __init void init_page_owner(void)
/* Initialize dummy and failure stacks and link them to stack_list */
dummy_stack.stack_record = __stack_depot_get_stack_record(dummy_handle);
failure_stack.stack_record = __stack_depot_get_stack_record(failure_handle);
- refcount_set(&dummy_stack.stack_record->count, 1);
- refcount_set(&failure_stack.stack_record->count, 1);
+ if (dummy_stack.stack_record)
+ refcount_set(&dummy_stack.stack_record->count, 1);
+ if (failure_stack.stack_record)
+ refcount_set(&failure_stack.stack_record->count, 1);
dummy_stack.next = &failure_stack;
stack_list = &dummy_stack;
}
@@ -856,6 +858,9 @@ static int stack_print(struct seq_file *m, void *v)
unsigned long nr_entries;
struct stack_record *stack_record = stack->stack_record;
+ if (!stack->stack_record)
+ return 0;
+
nr_entries = stack_record->size;
entries = stack_record->entries;
stack_count = refcount_read(&stack_record->count) - 1;
--
2.44.0
