From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Wed, 25 Dec 2019 17:50:53 +0000 (+0100)
Subject: start: remove procfs pidfd support
X-Git-Tag: lxc-4.0.0~63^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b94283e19f19495d6d853d43146f2c640542c751;p=thirdparty%2Flxc.git

start: remove procfs pidfd support

We'll only rely on proper anon-inode based pidfd support in the future.
There's no good reason to use the procfs fallback. All the fancy features we
might want to use are only available with anon-inode pidfds.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---

diff --git a/src/lxc/start.c b/src/lxc/start.c
index d62acf4bd..f085aa60d 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -385,8 +385,6 @@ static int signal_handler(int fd, uint32_t events, void *data,
 	if (siginfo.ssi_signo == SIGHUP) {
 		if (hdlr->pidfd >= 0)
 			lxc_raw_pidfd_send_signal(hdlr->pidfd, SIGTERM, NULL, 0);
-		else if (hdlr->proc_pidfd >= 0)
-			lxc_raw_pidfd_send_signal(hdlr->proc_pidfd, SIGTERM, NULL, 0);
 		else
 			kill(hdlr->pid, SIGTERM);
 		INFO("Killing %d since terminal hung up", hdlr->pid);
@@ -398,9 +396,6 @@ static int signal_handler(int fd, uint32_t events, void *data,
 		if (hdlr->pidfd >= 0)
 			lxc_raw_pidfd_send_signal(hdlr->pidfd,
 						  siginfo.ssi_signo, NULL, 0);
-		else if (hdlr->proc_pidfd >= 0)
-			lxc_raw_pidfd_send_signal(hdlr->proc_pidfd,
-						  siginfo.ssi_signo, NULL, 0);
 		else
 			kill(hdlr->pid, siginfo.ssi_signo);
 		INFO("Forwarded signal %d to pid %d", siginfo.ssi_signo, hdlr->pid);
@@ -649,8 +644,6 @@ void lxc_zero_handler(struct lxc_handler *handler)
 
 	handler->pidfd = -EBADF;
 
-	handler->proc_pidfd = -EBADF;
-
 	handler->sigfd = -1;
 
 	for (i = 0; i < LXC_NS_MAX; i++)
@@ -674,9 +667,6 @@ void lxc_free_handler(struct lxc_handler *handler)
 	if (handler->pidfd >= 0)
 		close(handler->pidfd);
 
-	if (handler->proc_pidfd >= 0)
-		close(handler->proc_pidfd);
-
 	if (handler->sigfd >= 0)
 		close(handler->sigfd);
 
@@ -726,7 +716,6 @@ struct lxc_handler *lxc_init_handler(const char *name, struct lxc_conf *conf,
 	handler->monitor_status_fd = -EBADF;
 	handler->pinfd = -1;
 	handler->pidfd = -EBADF;
-	handler->proc_pidfd = -EBADF;
 	handler->sigfd = -EBADF;
 	handler->init_died = false;
 	handler->state_socket_pair[0] = handler->state_socket_pair[1] = -1;
@@ -1104,8 +1093,6 @@ void lxc_abort(const char *name, struct lxc_handler *handler)
 
 	if (handler->pidfd >= 0)
 		ret = lxc_raw_pidfd_send_signal(handler->pidfd, SIGKILL, NULL, 0);
-	else if (handler->proc_pidfd >= 0)
-		ret = lxc_raw_pidfd_send_signal(handler->proc_pidfd, SIGKILL, NULL, 0);
 	else if (handler->pid > 0)
 		ret = kill(handler->pid, SIGKILL);
 	if (ret < 0)
@@ -1624,30 +1611,6 @@ static inline int do_share_ns(void *arg)
 	return 0;
 }
 
-static int proc_pidfd_open(pid_t pid)
-{
-	__do_close_prot_errno int proc_pidfd = -EBADF;
-	char path[100];
-
-	snprintf(path, sizeof(path), "/proc/%d", pid);
-	proc_pidfd = open(path, O_DIRECTORY | O_RDONLY | O_CLOEXEC);
-	if (proc_pidfd < 0) {
-		SYSERROR("Failed to open %s", path);
-		return -1;
-	}
-
-	/* Test whether we can send signals. */
-	if (lxc_raw_pidfd_send_signal(proc_pidfd, 0, NULL, 0)) {
-		if (errno != ENOSYS)
-			SYSERROR("Failed to send signal through pidfd");
-		else
-			INFO("Sending signals through pidfds not supported on this kernel");
-		return -1;
-	}
-
-	return move_fd(proc_pidfd);
-}
-
 /* lxc_spawn() performs crucial setup tasks and clone()s the new process which
  * exec()s the requested container binary.
  * Note that lxc_spawn() runs in the parent namespaces. Any operations performed
@@ -1759,12 +1722,6 @@ static int lxc_spawn(struct lxc_handler *handler)
 	}
 	TRACE("Cloned child process %d", handler->pid);
 
-	if (handler->pidfd < 0) {
-		handler->proc_pidfd = proc_pidfd_open(handler->pid);
-		if (handler->proc_pidfd < 0 && (errno != ENOSYS))
-			goto out_delete_net;
-	}
-
 	ret = snprintf(pidstr, 20, "%d", handler->pid);
 	if (ret < 0 || ret >= 20)
 		goto out_delete_net;
diff --git a/src/lxc/start.h b/src/lxc/start.h
index 662ac5570..f40b4d661 100644
--- a/src/lxc/start.h
+++ b/src/lxc/start.h
@@ -83,12 +83,6 @@ struct lxc_handler {
 	/* The child's pidfd. */
 	int pidfd;
 
-	/*
-	 * File descriptor for the /proc/<pid> directory of the container's
-	 * init process.
-	 */
-	int proc_pidfd;
-
 	/* The grandfather's pid when double-forking. */
 	pid_t transient_pid;