From 245cfbcd3d3b298c75e01946262b3ff2cf7d0796 Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Tue, 18 Nov 2025 21:05:54 -0800 Subject: [PATCH] perf maps: Avoid RC_CHK use after free The case of __maps__fixup_overlap_and_insert where the "new" maps covers existing mappings can create a use-after-free with reference count checking enabled. The issue is that "pos" holds a map pointer from maps_by_address that is put from maps_by_address but then used to look for a map in maps_by_name (the compared map is now a use-after-free). The issue stems from using maps__remove which redoes some of the searches already done by __maps__fixup_overlap_and_insert, so optimize the code (by avoiding repeated searches) and avoid the use-after-free by inlining the appropriate removal code. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202511141407.f9edcfa6-lkp@intel.com Signed-off-by: Ian Rogers Reviewed-by: James Clark Signed-off-by: Namhyung Kim --- tools/perf/util/maps.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c index 779f6230130af..c321d4f4d8466 100644 --- a/tools/perf/util/maps.c +++ b/tools/perf/util/maps.c @@ -931,8 +931,9 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new) return err; } else { struct map *next = NULL; + unsigned int nr_maps = maps__nr_maps(maps); - if (i + 1 < maps__nr_maps(maps)) + if (i + 1 < nr_maps) next = maps_by_address[i + 1]; if (!next || map__start(next) >= map__end(new)) { @@ -953,7 +954,24 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new) check_invariants(maps); return err; } - __maps__remove(maps, pos); + /* + * pos fully covers the previous mapping so remove + * it. The following is an inlined version of + * maps__remove that reuses the already computed + * indices. + */ + map__put(maps_by_address[i]); + memmove(&maps_by_address[i], + &maps_by_address[i + 1], + (nr_maps - i - 1) * sizeof(*maps_by_address)); + + if (maps_by_name) { + map__put(maps_by_name[ni]); + memmove(&maps_by_name[ni], + &maps_by_name[ni + 1], + (nr_maps - ni - 1) * sizeof(*maps_by_name)); + } + --RC_CHK_ACCESS(maps)->nr_maps; check_invariants(maps); /* * Maps are ordered but no need to increase `i` as the -- 2.47.3