systemd/0377-flush_ports-flush-POSIX-message-queues-properly.patch
Jan Macku ee560ada81 systemd-257-12
Resolves: RHEL-100553,RHEL-103354,RHEL-104555,RHEL-106260,RHEL-44419,RHEL-72701,RHEL-79976,RHEL-97625,RHEL-97762
2025-08-13 13:54:24 +02:00

120 lines
3.8 KiB
Diff

From b2cbc7591414472269260470798e3d0feccdb1f9 Mon Sep 17 00:00:00 2001
From: "Todd C. Miller" <Todd.Miller@sudo.ws>
Date: Tue, 6 May 2025 16:39:14 -0600
Subject: [PATCH] flush_ports: flush POSIX message queues properly
On Linux, read() on a message queue descriptor returns the message
queue statistics, not the actual message queue data. We need to use
mq_receive() to drain the queues instead.
Fixes a problem where a POSIX message queue socket unit with messages
in the queue at shutdown time could result in a hang on reboot/shutdown.
(cherry picked from commit ffb6adb76367d5ab7d43937ccaac5947717b5b78)
Resolves: RHEL-100553
---
src/basic/socket-util.c | 49 +++++++++++++++++++++++++++++++++++++++++
src/basic/socket-util.h | 1 +
src/core/socket.c | 8 +++++--
3 files changed, 56 insertions(+), 2 deletions(-)
diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index 94089323b4..5c8c788846 100644
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -5,6 +5,7 @@
#include <arpa/inet.h>
#include <errno.h>
#include <limits.h>
+#include <mqueue.h>
#include <netdb.h>
#include <netinet/ip.h>
#include <poll.h>
@@ -1296,6 +1297,54 @@ int flush_accept(int fd) {
}
}
+ssize_t flush_mqueue(int fd) {
+ _cleanup_free_ char *buf = NULL;
+ struct mq_attr attr;
+ ssize_t count = 0;
+ int r;
+
+ assert(fd >= 0);
+
+ /* Similar to flush_fd() but flushes all messages from a POSIX message queue. */
+
+ for (;;) {
+ ssize_t l;
+
+ r = fd_wait_for_event(fd, POLLIN, /* timeout= */ 0);
+ if (r < 0) {
+ if (r == -EINTR)
+ continue;
+
+ return r;
+ }
+ if (r == 0)
+ return count;
+
+ if (!buf) {
+ /* Buffer must be at least as large as mq_msgsize. */
+ if (mq_getattr(fd, &attr) < 0)
+ return -errno;
+
+ buf = malloc(attr.mq_msgsize);
+ if (!buf)
+ return -ENOMEM;
+ }
+
+ l = mq_receive(fd, buf, attr.mq_msgsize, /* msg_prio = */ NULL);
+ if (l < 0) {
+ if (errno == EINTR)
+ continue;
+
+ if (errno == EAGAIN)
+ return count;
+
+ return -errno;
+ }
+
+ count += l;
+ }
+}
+
struct cmsghdr* cmsg_find(struct msghdr *mh, int level, int type, socklen_t length) {
struct cmsghdr *cmsg;
diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
index 874e559a4b..013edf0d4f 100644
--- a/src/basic/socket-util.h
+++ b/src/basic/socket-util.h
@@ -197,6 +197,7 @@ int receive_many_fds(int transport_fd, int **ret_fds_array, size_t *ret_n_fds_ar
ssize_t next_datagram_size_fd(int fd);
int flush_accept(int fd);
+ssize_t flush_mqueue(int fd);
#define CMSG_FOREACH(cmsg, mh) \
for ((cmsg) = CMSG_FIRSTHDR(mh); (cmsg); (cmsg) = CMSG_NXTHDR((mh), (cmsg)))
diff --git a/src/core/socket.c b/src/core/socket.c
index 6599527515..1e224b2407 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -2295,8 +2295,12 @@ static void flush_ports(Socket *s) {
if (p->fd < 0)
continue;
- (void) flush_accept(p->fd);
- (void) flush_fd(p->fd);
+ if (p->type == SOCKET_MQUEUE)
+ (void) flush_mqueue(p->fd);
+ else {
+ (void) flush_accept(p->fd);
+ (void) flush_fd(p->fd);
+ }
}
}