Daniel Borkmann says:

====================
bpf-next 2022-11-25

We've added 101 non-merge commits during the last 11 day(s) which contain
a total of 109 files changed, 8827 insertions(+), 1129 deletions(-).

The main changes are:

1) Support for user defined BPF objects: the use case is to allocate own
   objects, build own object hierarchies and use the building blocks to
   build own data structures flexibly, for example, linked lists in BPF,
   from Kumar Kartikeya Dwivedi.

2) Add bpf_rcu_read_{,un}lock() support for sleepable programs,
   from Yonghong Song.

3) Add support storing struct task_struct objects as kptrs in maps,
   from David Vernet.

4) Batch of BPF map documentation improvements, from Maryam Tahhan
   and Donald Hunter.

5) Improve BPF verifier to propagate nullness information for branches
   of register to register comparisons, from Eduard Zingerman.

6) Fix cgroup BPF iter infra to hold reference on the start cgroup,
   from Hou Tao.

7) Fix BPF verifier to not mark fentry/fexit program arguments as trusted
   given it is not the case for them, from Alexei Starovoitov.

8) Improve BPF verifier's realloc handling to better play along with dynamic
   runtime analysis tools like KASAN and friends, from Kees Cook.

9) Remove legacy libbpf mode support from bpftool,
   from Sahid Orentino Ferdjaoui.

10) Rework zero-len skb redirection checks to avoid potentially breaking
    existing BPF test infra users, from Stanislav Fomichev.

11) Two small refactorings which are independent and have been split out
    of the XDP queueing RFC series, from Toke Høiland-Jørgensen.

12) Fix a memory leak in LSM cgroup BPF selftest, from Wang Yufen.

13) Documentation on how to run BPF CI without patch submission,
    from Daniel Müller.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
====================

Link: https://lore.kernel.org/r/20221125012450.441-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 76 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
index c4a2adb38da1..e02feb5fae97 100644
--- a/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
@@ -189,6 +189,80 @@ static void test_walk_self_only(struct cgroup_iter *skel)
 			      BPF_CGROUP_ITER_SELF_ONLY, "self_only");
 }
 
+static void test_walk_dead_self_only(struct cgroup_iter *skel)
+{
+	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+	char expected_output[128], buf[128];
+	const char *cgrp_name = "/dead";
+	union bpf_iter_link_info linfo;
+	int len, cgrp_fd, iter_fd;
+	struct bpf_link *link;
+	size_t left;
+	char *p;
+
+	cgrp_fd = create_and_get_cgroup(cgrp_name);
+	if (!ASSERT_GE(cgrp_fd, 0, "create cgrp"))
+		return;
+
+	/* The cgroup will be dead during read() iteration, so it only has
+	 * epilogue in the output
+	 */
+	snprintf(expected_output, sizeof(expected_output), EPILOGUE);
+
+	memset(&linfo, 0, sizeof(linfo));
+	linfo.cgroup.cgroup_fd = cgrp_fd;
+	linfo.cgroup.order = BPF_CGROUP_ITER_SELF_ONLY;
+	opts.link_info = &linfo;
+	opts.link_info_len = sizeof(linfo);
+
+	link = bpf_program__attach_iter(skel->progs.cgroup_id_printer, &opts);
+	if (!ASSERT_OK_PTR(link, "attach_iter"))
+		goto close_cgrp;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(link));
+	if (!ASSERT_GE(iter_fd, 0, "iter_create"))
+		goto free_link;
+
+	/* Close link fd and cgroup fd */
+	bpf_link__destroy(link);
+	close(cgrp_fd);
+
+	/* Remove cgroup to mark it as dead */
+	remove_cgroup(cgrp_name);
+
+	/* Two kern_sync_rcu() and usleep() pairs are used to wait for the
+	 * releases of cgroup css, and the last kern_sync_rcu() and usleep()
+	 * pair is used to wait for the free of cgroup itself.
+	 */
+	kern_sync_rcu();
+	usleep(8000);
+	kern_sync_rcu();
+	usleep(8000);
+	kern_sync_rcu();
+	usleep(1000);
+
+	memset(buf, 0, sizeof(buf));
+	left = ARRAY_SIZE(buf);
+	p = buf;
+	while ((len = read(iter_fd, p, left)) > 0) {
+		p += len;
+		left -= len;
+	}
+
+	ASSERT_STREQ(buf, expected_output, "dead cgroup output");
+
+	/* read() after iter finishes should be ok. */
+	if (len == 0)
+		ASSERT_OK(read(iter_fd, buf, sizeof(buf)), "second_read");
+
+	close(iter_fd);
+	return;
+free_link:
+	bpf_link__destroy(link);
+close_cgrp:
+	close(cgrp_fd);
+}
+
 void test_cgroup_iter(void)
 {
 	struct cgroup_iter *skel = NULL;
@@ -217,6 +291,8 @@ void test_cgroup_iter(void)
 		test_early_termination(skel);
 	if (test__start_subtest("cgroup_iter__self_only"))
 		test_walk_self_only(skel);
+	if (test__start_subtest("cgroup_iter__dead_self_only"))
+		test_walk_dead_self_only(skel);
 out:
 	cgroup_iter__destroy(skel);
 	cleanup_cgroups();