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selftests/bpf: Fix flaky test btf_map_in_map/lookup_update 

[ Upstream commit 14bb1e8c8d ]

Recently, I frequently hit the following test failure:

  [root@arch-fb-vm1 bpf]# ./test_progs -n 33/1
  test_lookup_update:PASS:skel_open 0 nsec
  [...]
  test_lookup_update:PASS:sync_rcu 0 nsec
  test_lookup_update:FAIL:map1_leak inner_map1 leaked!
  #33/1    btf_map_in_map/lookup_update:FAIL
  #33      btf_map_in_map:FAIL

In the test, after map is closed and then after two rcu grace periods,
it is assumed that map_id is not available to user space.

But the above assumption cannot be guaranteed. After zero or one
or two rcu grace periods in different siturations, the actual
freeing-map-work is put into a workqueue. Later on, when the work
is dequeued, the map will be actually freed.
See bpf_map_put() in kernel/bpf/syscall.c.

By using workqueue, there is no ganrantee that map will be actually
freed after a couple of rcu grace periods. This patch removed
such map leak detection and then the test can pass consistently.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240322061353.632136-1-yonghong.song@linux.dev
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Yonghong Song 2024-03-21 23:13:53 -07:00 committed by Greg Kroah-Hartman
parent 9233170689
commit 4a6adfe5a7
1 changed files with 1 additions and 25 deletions
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26
tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c
View File

@ -25,7 +25,7 @@ static void test_lookup_update(void)
int map1_fd, map2_fd, map3_fd, map4_fd, map5_fd, map1_id, map2_id;
int outer_arr_fd, outer_hash_fd, outer_arr_dyn_fd;
struct test_btf_map_in_map *skel;
int err, key = 0, val, i, fd;
int err, key = 0, val, i;
skel = test_btf_map_in_map__open_and_load();
if (CHECK(!skel, "skel_open", "failed to open&load skeleton\n"))
@ -102,30 +102,6 @@ static void test_lookup_update(void)
CHECK(map1_id == 0, "map1_id", "failed to get ID 1\n");
CHECK(map2_id == 0, "map2_id", "failed to get ID 2\n");
test_btf_map_in_map__destroy(skel);
skel = NULL;
/* we need to either wait for or force synchronize_rcu(), before
* checking for "still exists" condition, otherwise map could still be
* resolvable by ID, causing false positives.
*
* Older kernels (5.8 and earlier) freed map only after two
* synchronize_rcu()s, so trigger two, to be entirely sure.
*/
CHECK(kern_sync_rcu(), "sync_rcu", "failed\n");
CHECK(kern_sync_rcu(), "sync_rcu", "failed\n");
fd = bpf_map_get_fd_by_id(map1_id);
if (CHECK(fd >= 0, "map1_leak", "inner_map1 leaked!\n")) {
close(fd);
goto cleanup;
}
fd = bpf_map_get_fd_by_id(map2_id);
if (CHECK(fd >= 0, "map2_leak", "inner_map2 leaked!\n")) {
close(fd);
goto cleanup;
}
cleanup:
test_btf_map_in_map__destroy(skel);
}