From: Matteo Croce <teknoraver@xxxxxxxx> In the BPF token example, the fsopen() syscall is called as privileged user. This is unneeded because fsopen() can be called also as unprivileged user from the user namespace. As the `fs_fd` file descriptor which was sent back and fort is still the same, keep it open instead of cloning and closing it twice via SCM_RIGHTS. cfr. https://github.com/systemd/systemd/pull/36134 Signed-off-by: Matteo Croce <teknoraver@xxxxxxxx> --- .../testing/selftests/bpf/prog_tests/token.c | 41 ++++++++++--------- 1 file changed, 21 insertions(+), 20 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c index f9392df23f8a..cfc032b910c4 100644 --- a/tools/testing/selftests/bpf/prog_tests/token.c +++ b/tools/testing/selftests/bpf/prog_tests/token.c @@ -115,7 +115,7 @@ static int create_bpffs_fd(void) static int materialize_bpffs_fd(int fs_fd, struct bpffs_opts *opts) { - int mnt_fd, err; + int err; /* set up token delegation mount options */ err = set_delegate_mask(fs_fd, "delegate_cmds", opts->cmds, opts->cmds_str); @@ -136,12 +136,7 @@ static int materialize_bpffs_fd(int fs_fd, struct bpffs_opts *opts) if (err < 0) return -errno; - /* create O_PATH fd for detached mount */ - mnt_fd = sys_fsmount(fs_fd, 0, 0); - if (err < 0) - return -errno; - - return mnt_fd; + return 0; } /* send FD over Unix domain (AF_UNIX) socket */ @@ -287,6 +282,7 @@ static void child(int sock_fd, struct bpffs_opts *opts, child_callback_fn callba { int mnt_fd = -1, fs_fd = -1, err = 0, bpffs_fd = -1, token_fd = -1; struct token_lsm *lsm_skel = NULL; + char one; /* load and attach LSM "policy" before we go into unpriv userns */ lsm_skel = token_lsm__open_and_load(); @@ -333,13 +329,19 @@ static void child(int sock_fd, struct bpffs_opts *opts, child_callback_fn callba err = sendfd(sock_fd, fs_fd); if (!ASSERT_OK(err, "send_fs_fd")) goto cleanup; - zclose(fs_fd); + + /* wait that the parent reads the fd, does the fsconfig() calls + * and send us a signal that it is done + */ + err = read(sock_fd, &one, sizeof(one)); + if (!ASSERT_GE(err, 0, "read_one")) + goto cleanup; /* avoid mucking around with mount namespaces and mounting at - * well-known path, just get detach-mounted BPF FS fd back from parent + * well-known path, just create O_PATH fd for detached mount */ - err = recvfd(sock_fd, &mnt_fd); - if (!ASSERT_OK(err, "recv_mnt_fd")) + mnt_fd = sys_fsmount(fs_fd, 0, 0); + if (!ASSERT_OK_FD(mnt_fd, "mnt_fd")) goto cleanup; /* try to fspick() BPF FS and try to add some delegation options */ @@ -429,24 +431,24 @@ static int wait_for_pid(pid_t pid) static void parent(int child_pid, struct bpffs_opts *bpffs_opts, int sock_fd) { - int fs_fd = -1, mnt_fd = -1, token_fd = -1, err; + int fs_fd = -1, token_fd = -1, err; + char one = 1; err = recvfd(sock_fd, &fs_fd); if (!ASSERT_OK(err, "recv_bpffs_fd")) goto cleanup; - mnt_fd = materialize_bpffs_fd(fs_fd, bpffs_opts); - if (!ASSERT_GE(mnt_fd, 0, "materialize_bpffs_fd")) { + err = materialize_bpffs_fd(fs_fd, bpffs_opts); + if (!ASSERT_GE(err, 0, "materialize_bpffs_fd")) { err = -EINVAL; goto cleanup; } - zclose(fs_fd); - /* pass BPF FS context object to parent */ - err = sendfd(sock_fd, mnt_fd); - if (!ASSERT_OK(err, "send_mnt_fd")) + /* notify the child that we did the fsconfig() calls and it can proceed. */ + err = write(sock_fd, &one, sizeof(one)); + if (!ASSERT_EQ(err, sizeof(one), "send_one")) goto cleanup; - zclose(mnt_fd); + zclose(fs_fd); /* receive BPF token FD back from child for some extra tests */ err = recvfd(sock_fd, &token_fd); @@ -459,7 +461,6 @@ static void parent(int child_pid, struct bpffs_opts *bpffs_opts, int sock_fd) cleanup: zclose(sock_fd); zclose(fs_fd); - zclose(mnt_fd); zclose(token_fd); if (child_pid > 0) -- 2.50.0
