[PATCH v3 02/10] mm/kmemleak: use stack_depot_fetch_into() for leak reports

[Matt Fleming <matt@readmodwrite.com>]

From: Caleb Kan <ckan@cloudflare.com>

kmemleak stores allocation backtraces as persistent stack depot handles.
With compressed frames, stack_depot_fetch() cannot return a pointer
to unsigned long stack-record entries, so leak reports would omit the
saved backtrace.

Use stack_depot_fetch_into() with a MAX_TRACE-sized local array before
formatting the report. MAX_TRACE matches the save-side limit, so every
valid kmemleak trace fits without truncation. Preserve frame order and the
existing report format.

Signed-off-by: Caleb Kan <ckan@cloudflare.com>
[mfleming: reworded for compressed frames]
Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
---
 mm/kmemleak.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 20c0eb41c873..61ff4a10ce11 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -378,10 +378,10 @@ static void __print_unreferenced(struct seq_file *seq,
 				 bool hex_dump)
 {
 	int i;
-	unsigned long *entries;
+	unsigned long entries[MAX_TRACE];
 	unsigned int nr_entries;
 
-	nr_entries = stack_depot_fetch(object->trace_handle, &entries);
+	nr_entries = stack_depot_fetch_into(object->trace_handle, entries, ARRAY_SIZE(entries));
 	warn_or_seq_printf(seq, "unreferenced object%s 0x%08lx (size %zu):\n",
 			   __object_type_str(object),
 			   object->pointer, object->size);
-- 
2.43.0