From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Dmitry V. Levin" Subject: [PATCH 2/2] samples: make pidfd-metadata fail gracefully on older kernels Date: Sun, 23 Jun 2019 14:28:00 +0300 Message-ID: <20190623112800.GB20697@altlinux.org> References: <20190620103105.cdxgqfelzlnkmblv@brauner.io> <20190620110037.GA4998@altlinux.org> <20190620111036.asi3mbcv4ax5ekrw@brauner.io> <20190621170613.GA26182@altlinux.org> <20190621221339.6yj4vg4zexv4y2j7@brauner.io> <20190623112717.GA20697@altlinux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190623112717.GA20697@altlinux.org> Sender: linux-kernel-owner@vger.kernel.org To: Christian Brauner Cc: Jann Horn , Oleg Nesterov , Arnd Bergmann , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-api@vger.kernel.org Initialize pidfd to an invalid descriptor, to fail gracefully on those kernels that do not implement CLONE_PIDFD and leave pidfd unchanged. Signed-off-by: Dmitry V. Levin --- samples/pidfd/pidfd-metadata.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/samples/pidfd/pidfd-metadata.c b/samples/pidfd/pidfd-metadata.c index 14b454448429..c459155daf9a 100644 --- a/samples/pidfd/pidfd-metadata.c +++ b/samples/pidfd/pidfd-metadata.c @@ -83,7 +83,7 @@ static int pidfd_metadata_fd(pid_t pid, int pidfd) int main(int argc, char *argv[]) { - int pidfd = 0, ret = EXIT_FAILURE; + int pidfd = -1, ret = EXIT_FAILURE; char buf[4096] = { 0 }; pid_t pid; int procfd, statusfd; @@ -91,7 +91,11 @@ int main(int argc, char *argv[]) pid = pidfd_clone(CLONE_PIDFD, &pidfd); if (pid < 0) - exit(ret); + err(ret, "CLONE_PIDFD"); + if (pidfd == -1) { + warnx("CLONE_PIDFD is not supported by the kernel"); + goto out; + } procfd = pidfd_metadata_fd(pid, pidfd); close(pidfd); -- ldv