diff options
| author | Lorenz Bauer <lmb@cloudflare.com> | 2020-06-08 17:22:01 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-06-09 11:21:43 -0700 |
| commit | 248e00ac47d64e153b9c50f45aad73cd61894a73 (patch) | |
| tree | c319d492bd9e0bf5c9c3c7a321af5036fa50fcaf | |
| parent | 26afa0a4eb3fd87757f9de56ec5db5a03b14e120 (diff) | |
| download | linux-248e00ac47d64e153b9c50f45aad73cd61894a73.tar.bz2 | |
bpf: cgroup: Allow multi-attach program to replace itself
When using BPF_PROG_ATTACH to attach a program to a cgroup in
BPF_F_ALLOW_MULTI mode, it is not possible to replace a program
with itself. This is because the check for duplicate programs
doesn't take the replacement program into account.
Replacing a program with itself might seem weird, but it has
some uses: first, it allows resetting the associated cgroup storage.
Second, it makes the API consistent with the non-ALLOW_MULTI usage,
where it is possible to replace a program with itself. Third, it
aligns BPF_PROG_ATTACH with bpf_link, where replacing itself is
also supported.
Sice this code has been refactored a few times this change will
only apply to v5.7 and later. Adjustments could be made to
commit 1020c1f24a94 ("bpf: Simplify __cgroup_bpf_attach") and
commit d7bf2c10af05 ("bpf: allocate cgroup storage entries on attaching bpf programs")
as well as commit 324bda9e6c5a ("bpf: multi program support for cgroup+bpf")
Fixes: af6eea57437a ("bpf: Implement bpf_link-based cgroup BPF program attachment")
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200608162202.94002-1-lmb@cloudflare.com
| -rw-r--r-- | kernel/bpf/cgroup.c | 2 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/prog_tests/cgroup_attach_multi.c | 7 |
2 files changed, 8 insertions, 1 deletions
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index fdf7836750a3..4d76f16524cc 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -378,7 +378,7 @@ static struct bpf_prog_list *find_attach_entry(struct list_head *progs, } list_for_each_entry(pl, progs, node) { - if (prog && pl->prog == prog) + if (prog && pl->prog == prog && prog != replace_prog) /* disallow attaching the same prog twice */ return ERR_PTR(-EINVAL); if (link && pl->link == link) diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_attach_multi.c b/tools/testing/selftests/bpf/prog_tests/cgroup_attach_multi.c index 139f8e82c7c6..b549fcfacc0b 100644 --- a/tools/testing/selftests/bpf/prog_tests/cgroup_attach_multi.c +++ b/tools/testing/selftests/bpf/prog_tests/cgroup_attach_multi.c @@ -230,6 +230,13 @@ void test_cgroup_attach_multi(void) "prog_replace", "errno=%d\n", errno)) goto err; + /* replace program with itself */ + attach_opts.replace_prog_fd = allow_prog[6]; + if (CHECK(bpf_prog_attach_xattr(allow_prog[6], cg1, + BPF_CGROUP_INET_EGRESS, &attach_opts), + "prog_replace", "errno=%d\n", errno)) + goto err; + value = 0; CHECK_FAIL(bpf_map_update_elem(map_fd, &key, &value, 0)); CHECK_FAIL(system(PING_CMD)); |