[PATCH v1 1/2] perf maps: Avoid RC_CHK use after free

[PATCH v1 1/2] perf maps: Avoid RC_CHK use after free

[Ian Rogers]

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 <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202511141407.f9edcfa6-lkp@intel.com
Signed-off-by: Ian Rogers <irogers@google.com>
---
 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 779f6230130a..c321d4f4d846 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
-- 
2.52.0.rc1.455.g30608eb744-goog

[PATCH v1 2/2] perf test maps: Additional maps__fixup_overlap_and_insert tests

[Ian Rogers]

Add additional test to the maps covering
maps__fixup_overlap_and_insert. Change the test suite to be for more
than just 1 test.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/builtin-test.c |  2 +-
 tools/perf/tests/maps.c         | 82 ++++++++++++++++++++++++++++++++-
 tools/perf/tests/tests.h        |  2 +-
 3 files changed, 83 insertions(+), 3 deletions(-)

diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 0d2fb7a4ae5b..9090e8238a44 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -126,7 +126,7 @@ static struct test_suite *generic_tests[] = {
 	&suite__jit_write_elf,
 	&suite__pfm,
 	&suite__api_io,
-	&suite__maps__merge_in,
+	&suite__maps,
 	&suite__demangle_java,
 	&suite__demangle_ocaml,
 	&suite__demangle_rust,
diff --git a/tools/perf/tests/maps.c b/tools/perf/tests/maps.c
index 4f1f9385ea9c..2c05d62f40dc 100644
--- a/tools/perf/tests/maps.c
+++ b/tools/perf/tests/maps.c
@@ -162,4 +162,84 @@ static int test__maps__merge_in(struct test_suite *t __maybe_unused, int subtest
 	return TEST_OK;
 }
 
-DEFINE_SUITE("maps__merge_in", maps__merge_in);
+static int test__maps__fixup_overlap_and_insert(struct test_suite *t __maybe_unused,
+						int subtest __maybe_unused)
+{
+	struct map_def initial_maps[] = {
+		{ "target_map", 1000, 2000 },
+		{ "next_map",   3000, 4000 },
+	};
+	struct map_def insert_split = { "split_map", 1400, 1600 };
+	struct map_def expected_after_split[] = {
+		{ "target_map", 1000, 1400 },
+		{ "split_map",  1400, 1600 },
+		{ "target_map", 1600, 2000 },
+		{ "next_map",   3000, 4000 },
+	};
+
+	struct map_def insert_eclipse = { "eclipse_map", 2500, 4500 };
+	struct map_def expected_final[] = {
+		{ "target_map",  1000, 1400 },
+		{ "split_map",   1400, 1600 },
+		{ "target_map",  1600, 2000 },
+		{ "eclipse_map", 2500, 4500 },
+		/* "next_map" (3000-4000) is removed */
+	};
+
+	struct map *map_split, *map_eclipse;
+	int ret;
+	unsigned int i;
+	struct maps *maps = maps__new(NULL);
+
+	TEST_ASSERT_VAL("failed to create maps", maps);
+
+	for (i = 0; i < ARRAY_SIZE(initial_maps); i++) {
+		struct map *map = dso__new_map(initial_maps[i].name);
+
+		TEST_ASSERT_VAL("failed to create map", map);
+		map__set_start(map, initial_maps[i].start);
+		map__set_end(map, initial_maps[i].end);
+		TEST_ASSERT_VAL("failed to insert map", maps__insert(maps, map) == 0);
+		map__put(map);
+	}
+
+	// Check splitting.
+	map_split = dso__new_map(insert_split.name);
+	TEST_ASSERT_VAL("failed to create split map", map_split);
+	map__set_start(map_split, insert_split.start);
+	map__set_end(map_split, insert_split.end);
+
+	ret = maps__fixup_overlap_and_insert(maps, map_split);
+	TEST_ASSERT_VAL("failed to fixup and insert split map", !ret);
+
+	map__zput(map_split);
+	ret = check_maps(expected_after_split, ARRAY_SIZE(expected_after_split), maps);
+	TEST_ASSERT_VAL("split check failed", !ret);
+
+	// Check cover 1 map with another.
+	map_eclipse = dso__new_map(insert_eclipse.name);
+	TEST_ASSERT_VAL("failed to create eclipse map", map_eclipse);
+	map__set_start(map_eclipse, insert_eclipse.start);
+	map__set_end(map_eclipse, insert_eclipse.end);
+
+	ret = maps__fixup_overlap_and_insert(maps, map_eclipse);
+	TEST_ASSERT_VAL("failed to fixup and insert eclipse map", !ret);
+
+	map__zput(map_eclipse);
+	ret = check_maps(expected_final, ARRAY_SIZE(expected_final), maps);
+	TEST_ASSERT_VAL("eclipse check failed", !ret);
+
+	maps__zput(maps);
+	return TEST_OK;
+}
+
+static struct test_case tests__maps[] = {
+	TEST_CASE("Test merge_in interface", maps__merge_in),
+	TEST_CASE("Test fix up overlap interface", maps__fixup_overlap_and_insert),
+	{	.name = NULL, }
+};
+
+struct test_suite suite__maps = {
+	.desc = "Maps - per process mmaps abstraction",
+	.test_cases = tests__maps,
+};
diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
index 33de16dde737..f5fba95b6f3f 100644
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -160,7 +160,7 @@ DECLARE_SUITE(bitmap_print);
 DECLARE_SUITE(perf_hooks);
 DECLARE_SUITE(unit_number__scnprint);
 DECLARE_SUITE(mem2node);
-DECLARE_SUITE(maps__merge_in);
+DECLARE_SUITE(maps);
 DECLARE_SUITE(time_utils);
 DECLARE_SUITE(jit_write_elf);
 DECLARE_SUITE(api_io);
-- 
2.52.0.rc1.455.g30608eb744-goog

Re: [PATCH v1 2/2] perf test maps: Additional maps__fixup_overlap_and_insert tests

[James Clark]

On 19/11/2025 5:05 am, Ian Rogers wrote:
> Add additional test to the maps covering
> maps__fixup_overlap_and_insert. Change the test suite to be for more
> than just 1 test.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>

Reviewed-by: James Clark <james.clark@linaro.org>

> ---
>   tools/perf/tests/builtin-test.c |  2 +-
>   tools/perf/tests/maps.c         | 82 ++++++++++++++++++++++++++++++++-
>   tools/perf/tests/tests.h        |  2 +-
>   3 files changed, 83 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
> index 0d2fb7a4ae5b..9090e8238a44 100644
> --- a/tools/perf/tests/builtin-test.c
> +++ b/tools/perf/tests/builtin-test.c
> @@ -126,7 +126,7 @@ static struct test_suite *generic_tests[] = {
>   	&suite__jit_write_elf,
>   	&suite__pfm,
>   	&suite__api_io,
> -	&suite__maps__merge_in,
> +	&suite__maps,
>   	&suite__demangle_java,
>   	&suite__demangle_ocaml,
>   	&suite__demangle_rust,
> diff --git a/tools/perf/tests/maps.c b/tools/perf/tests/maps.c
> index 4f1f9385ea9c..2c05d62f40dc 100644
> --- a/tools/perf/tests/maps.c
> +++ b/tools/perf/tests/maps.c
> @@ -162,4 +162,84 @@ static int test__maps__merge_in(struct test_suite *t __maybe_unused, int subtest
>   	return TEST_OK;
>   }
>   
> -DEFINE_SUITE("maps__merge_in", maps__merge_in);
> +static int test__maps__fixup_overlap_and_insert(struct test_suite *t __maybe_unused,
> +						int subtest __maybe_unused)
> +{
> +	struct map_def initial_maps[] = {
> +		{ "target_map", 1000, 2000 },
> +		{ "next_map",   3000, 4000 },
> +	};
> +	struct map_def insert_split = { "split_map", 1400, 1600 };
> +	struct map_def expected_after_split[] = {
> +		{ "target_map", 1000, 1400 },
> +		{ "split_map",  1400, 1600 },
> +		{ "target_map", 1600, 2000 },
> +		{ "next_map",   3000, 4000 },
> +	};
> +
> +	struct map_def insert_eclipse = { "eclipse_map", 2500, 4500 };
> +	struct map_def expected_final[] = {
> +		{ "target_map",  1000, 1400 },
> +		{ "split_map",   1400, 1600 },
> +		{ "target_map",  1600, 2000 },
> +		{ "eclipse_map", 2500, 4500 },
> +		/* "next_map" (3000-4000) is removed */
> +	};
> +
> +	struct map *map_split, *map_eclipse;
> +	int ret;
> +	unsigned int i;
> +	struct maps *maps = maps__new(NULL);
> +
> +	TEST_ASSERT_VAL("failed to create maps", maps);
> +
> +	for (i = 0; i < ARRAY_SIZE(initial_maps); i++) {
> +		struct map *map = dso__new_map(initial_maps[i].name);
> +
> +		TEST_ASSERT_VAL("failed to create map", map);
> +		map__set_start(map, initial_maps[i].start);
> +		map__set_end(map, initial_maps[i].end);
> +		TEST_ASSERT_VAL("failed to insert map", maps__insert(maps, map) == 0);
> +		map__put(map);
> +	}
> +
> +	// Check splitting.
> +	map_split = dso__new_map(insert_split.name);
> +	TEST_ASSERT_VAL("failed to create split map", map_split);
> +	map__set_start(map_split, insert_split.start);
> +	map__set_end(map_split, insert_split.end);
> +
> +	ret = maps__fixup_overlap_and_insert(maps, map_split);
> +	TEST_ASSERT_VAL("failed to fixup and insert split map", !ret);
> +
> +	map__zput(map_split);
> +	ret = check_maps(expected_after_split, ARRAY_SIZE(expected_after_split), maps);
> +	TEST_ASSERT_VAL("split check failed", !ret);
> +
> +	// Check cover 1 map with another.
> +	map_eclipse = dso__new_map(insert_eclipse.name);
> +	TEST_ASSERT_VAL("failed to create eclipse map", map_eclipse);
> +	map__set_start(map_eclipse, insert_eclipse.start);
> +	map__set_end(map_eclipse, insert_eclipse.end);
> +
> +	ret = maps__fixup_overlap_and_insert(maps, map_eclipse);
> +	TEST_ASSERT_VAL("failed to fixup and insert eclipse map", !ret);
> +
> +	map__zput(map_eclipse);
> +	ret = check_maps(expected_final, ARRAY_SIZE(expected_final), maps);
> +	TEST_ASSERT_VAL("eclipse check failed", !ret);
> +
> +	maps__zput(maps);
> +	return TEST_OK;
> +}
> +
> +static struct test_case tests__maps[] = {
> +	TEST_CASE("Test merge_in interface", maps__merge_in),
> +	TEST_CASE("Test fix up overlap interface", maps__fixup_overlap_and_insert),
> +	{	.name = NULL, }
> +};
> +
> +struct test_suite suite__maps = {
> +	.desc = "Maps - per process mmaps abstraction",
> +	.test_cases = tests__maps,
> +};
> diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
> index 33de16dde737..f5fba95b6f3f 100644
> --- a/tools/perf/tests/tests.h
> +++ b/tools/perf/tests/tests.h
> @@ -160,7 +160,7 @@ DECLARE_SUITE(bitmap_print);
>   DECLARE_SUITE(perf_hooks);
>   DECLARE_SUITE(unit_number__scnprint);
>   DECLARE_SUITE(mem2node);
> -DECLARE_SUITE(maps__merge_in);
> +DECLARE_SUITE(maps);
>   DECLARE_SUITE(time_utils);
>   DECLARE_SUITE(jit_write_elf);
>   DECLARE_SUITE(api_io);

Re: [PATCH v1 1/2] perf maps: Avoid RC_CHK use after free

[James Clark]

On 19/11/2025 5:05 am, Ian Rogers wrote:
> 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 <oliver.sang@intel.com>
> Closes: https://lore.kernel.org/oe-lkp/202511141407.f9edcfa6-lkp@intel.com
> Signed-off-by: Ian Rogers <irogers@google.com>

Reviewed-by: James Clark <james.clark@linaro.org>

> ---
>   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 779f6230130a..c321d4f4d846 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

Re: [PATCH v1 1/2] perf maps: Avoid RC_CHK use after free

[Namhyung Kim]

On Tue, 18 Nov 2025 21:05:54 -0800, Ian Rogers wrote:
> 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.
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung