Commit d937bc3449fa ("bpf: make uniform use of array->elem_size
everywhere in arraymap.c") changed array_map_gen_lookup to use
array->elem_size instead of round_up(map->value_size, 8) as the element
size when generating code to access a value in an array map.
array->elem_size, however, is not set by bpf_map_meta_alloc when
initializing an BPF_MAP_TYPE_ARRAY_OF_MAPS or BPF_MAP_TYPE_HASH_OF_MAPS.
This results in array_map_gen_lookup incorrectly outputting code that
always accesses index 0 in the array (as the index will be calculated
via a multiplication with the element size, which is incorrectly set to
0).
Set elem_size on the bpf_array object when allocating an array or hash
of maps and add a selftest that accesses an inner map at a nonzero index
to prevent regressions.
Fixes: d937bc3449fa ("bpf: make uniform use of array->elem_size everywhere in arraymap.c")
Signed-off-by: Rhys Rustad-Elliott <me@xxxxxxxxxx>
---
kernel/bpf/map_in_map.c | 8 +++-
.../map_in_map_inner_array_lookup.c | 33 ++++++++++++++
.../test_map_in_map_inner_array_lookup.c | 45 +++++++++++++++++++
3 files changed, 84 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/map_in_map_inner_array_lookup.c
create mode 100644 tools/testing/selftests/bpf/progs/test_map_in_map_inner_array_lookup.c
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 2c5c64c2a53b..8d65b12e0834 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -69,9 +69,13 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
/* Misc members not needed in bpf_map_meta_equal() check. */
inner_map_meta->ops = inner_map->ops;
if (inner_map->ops == &array_map_ops) {
+ struct bpf_array *inner_array_meta =
+ container_of(inner_map_meta, struct bpf_array, map);
+ struct bpf_array *inner_array = container_of(inner_map, struct bpf_array, map);
+
+ inner_array_meta->index_mask = inner_array->index_mask;
+ inner_array_meta->elem_size = round_up(inner_map->value_size, 8);
inner_map_meta->bypass_spec_v1 = inner_map->bypass_spec_v1;
- container_of(inner_map_meta, struct bpf_array, map)->index_mask =
- container_of(inner_map, struct bpf_array, map)->index_mask;
}
fdput(f);
diff --git a/tools/testing/selftests/bpf/prog_tests/map_in_map_inner_array_lookup.c b/tools/testing/selftests/bpf/prog_tests/map_in_map_inner_array_lookup.c
new file mode 100644
index 000000000000..264d4788e5fd
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/map_in_map_inner_array_lookup.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <test_progs.h>
+
+#include "test_map_in_map_inner_array_lookup.skel.h"
+
+static int duration;
+
+void test_map_in_map_inner_array_lookup(void)
+{
+ int map1_fd, err;
+ int key = 3;
+ int val = 1;
+ struct test_map_in_map_inner_array_lookup *skel;
+
+ skel = test_map_in_map_inner_array_lookup__open_and_load();
+ if (CHECK(!skel, "skel_open", "failed to open&load skeleton\n"))
+ return;
+
+ err = test_map_in_map_inner_array_lookup__attach(skel);
+ if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
+ goto cleanup;
+
+ map1_fd = bpf_map__fd(skel->maps.inner_map1);
+ bpf_map_update_elem(map1_fd, &key, &val, 0);
+ usleep(1);
+ /* Probe should have set the element at index 3 to 2 */
+ bpf_map_lookup_elem(map1_fd, &key, &val);
+ CHECK(val != 2, "inner1", "got %d != exp %d\n", val, 2);
+
+cleanup:
+ test_map_in_map_inner_array_lookup__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_map_in_map_inner_array_lookup.c b/tools/testing/selftests/bpf/progs/test_map_in_map_inner_array_lookup.c
new file mode 100644
index 000000000000..c2c8f2fa451d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_map_in_map_inner_array_lookup.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+struct inner_map {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 5);
+ __type(key, int);
+ __type(value, int);
+} inner_map1 SEC(".maps");
+
+struct outer_map {
+ __uint(type, BPF_MAP_TYPE_HASH_OF_MAPS);
+ __uint(max_entries, 3);
+ __type(key, int);
+ __array(values, struct inner_map);
+} outer_map1 SEC(".maps") = {
+ .values = {
+ [2] = &inner_map1,
+ },
+};
+
+SEC("raw_tp/sys_enter")
+int handle__sys_enter(void *ctx)
+{
+ int outer_key = 2, inner_key = 3;
+ int *val;
+ void *map;
+
+ map = bpf_map_lookup_elem(&outer_map1, &outer_key);
+ if (!map)
+ return 1;
+
+ val = bpf_map_lookup_elem(map, &inner_key);
+ if (!val)
+ return 1;
+
+ if (*val == 1)
+ *val = 2;
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.40.1
