linux-kernel - [PATCH v1] perf maps: Ensure kmap is set up for all inserts

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Message-ID: <20250914181808.1957729-1-irogers@google.com>
Date: Sun, 14 Sep 2025 11:18:08 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	"Liang, Kan" <kan.liang@...ux.intel.com>, Chun-Tse Shao <ctshao@...gle.com>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v1] perf maps: Ensure kmap is set up for all inserts

__maps__fixup_overlap_and_insert may split or directly insert a map,
when doing this the map may need to have a kmap set up for the sake of
the kmaps. The missing kmap set up fails the check_invariants test in
maps, later "Internal error" reports from map__kmap and ultimately
causes segfaults.

Similar fixes were added in commit e0e4e0b8b7fa ("perf maps: Add
missing map__set_kmap_maps() when replacing a kernel map") and commit
25d9c0301d36 ("perf maps: Set the kmaps for newly created/added kernel
maps") but they missed cases. To try to reduce the risk of this,
update the kmap directly following any manual insert. This identified
another problem in maps__copy_from.

Fixes: e0e4e0b8b7fa ("perf maps: Add missing map__set_kmap_maps() when replacing a kernel map")
Fixes: 25d9c0301d36 ("perf maps: Set the kmaps for newly created/added kernel maps")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/maps.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
index 85b2a93a59ac..779f6230130a 100644
--- a/tools/perf/util/maps.c
+++ b/tools/perf/util/maps.c
@@ -477,6 +477,7 @@ static int __maps__insert(struct maps *maps, struct map *new)
 	}
 	/* Insert the value at the end. */
 	maps_by_address[nr_maps] = map__get(new);
+	map__set_kmap_maps(new, maps);
 	if (maps_by_name)
 		maps_by_name[nr_maps] = map__get(new);
 
@@ -502,8 +503,6 @@ static int __maps__insert(struct maps *maps, struct map *new)
 	if (map__end(new) < map__start(new))
 		RC_CHK_ACCESS(maps)->ends_broken = true;
 
-	map__set_kmap_maps(new, maps);
-
 	return 0;
 }
 
@@ -891,6 +890,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 		if (before) {
 			map__put(maps_by_address[i]);
 			maps_by_address[i] = before;
+			map__set_kmap_maps(before, maps);
 
 			if (maps_by_name) {
 				map__put(maps_by_name[ni]);
@@ -918,6 +918,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 			 */
 			map__put(maps_by_address[i]);
 			maps_by_address[i] = map__get(new);
+			map__set_kmap_maps(new, maps);
 
 			if (maps_by_name) {
 				map__put(maps_by_name[ni]);
@@ -942,14 +943,13 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
 				 */
 				map__put(maps_by_address[i]);
 				maps_by_address[i] = map__get(new);
+				map__set_kmap_maps(new, maps);
 
 				if (maps_by_name) {
 					map__put(maps_by_name[ni]);
 					maps_by_name[ni] = map__get(new);
 				}
 
-				map__set_kmap_maps(new, maps);
-
 				check_invariants(maps);
 				return err;
 			}
@@ -1019,6 +1019,7 @@ int maps__copy_from(struct maps *dest, struct maps *parent)
 				err = unwind__prepare_access(dest, new, NULL);
 				if (!err) {
 					dest_maps_by_address[i] = new;
+					map__set_kmap_maps(new, dest);
 					if (dest_maps_by_name)
 						dest_maps_by_name[i] = map__get(new);
 					RC_CHK_ACCESS(dest)->nr_maps = i + 1;
-- 
2.51.0.384.g4c02a37b29-goog