From 39e5e97e68a9c1bca3bcfa6c9316a83dad0b072d Mon Sep 17 00:00:00 2001
From: Franck Bui <fbui@suse.com>
Date: Thu, 29 Sep 2016 19:44:34 +0200
Subject: [PATCH] pid1: don't return any error in manager_dispatch_notify_fd()
 (#4240)

If manager_dispatch_notify_fd() fails and returns an error then the handling of
service notifications will be disabled entirely leading to a compromised system.

For example pid1 won't be able to receive the WATCHDOG messages anymore and
will kill all services supposed to send such messages.
(cherry picked from commit 9987750e7a4c62e0eb8473603150596ba7c3a015)
---
 src/core/manager.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/core/manager.c b/src/core/manager.c
index a085ed899a..36488b673a 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -1643,10 +1643,14 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
 
         n = recvmsg(m->notify_fd, &msghdr, MSG_DONTWAIT|MSG_CMSG_CLOEXEC);
         if (n < 0) {
-                if (errno == EAGAIN || errno == EINTR)
-                        return 0;
+                if (!IN_SET(errno, EAGAIN, EINTR))
+                        log_error("Failed to receive notification message: %m");
 
-                return -errno;
+                /* It's not an option to return an error here since it
+                 * would disable the notification handler entirely. Services
+                 * wouldn't be able to send the WATCHDOG message for
+                 * example... */
+                return 0;
         }
         if (n == 0) {
                 log_debug("Got zero-length notification message. Ignoring.");
@@ -1673,7 +1677,8 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
                 r = fdset_new_array(&fds, fd_array, n_fds);
                 if (r < 0) {
                         close_many(fd_array, n_fds);
-                        return log_oom();
+                        log_oom();
+                        return 0;
                 }
         }