From: Maciej Wereski <m.wereski@partner.samsung.com>
Date: Tue, 8 Sep 2015 13:36:30 +0000 (+0200)
Subject: sd_pid_notify_with_fds: fix computing msg_controllen
X-Git-Tag: v227.2^2~43
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=bfe9c16671c456eb4c12e0ec01564c43a73c3127

sd_pid_notify_with_fds: fix computing msg_controllen

CMSG_SPACE(0) may return value other than 0. This caused sendmsg to fail
with EINVAL, when have_pid or n_fds was 0.
---

diff --git a/src/libelogind/sd-daemon/sd-daemon.c b/src/libelogind/sd-daemon/sd-daemon.c
index 7639b6d3b..f74f44c65 100644
--- a/src/libelogind/sd-daemon/sd-daemon.c
+++ b/src/libelogind/sd-daemon/sd-daemon.c
@@ -406,8 +406,9 @@ _public_ int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char
         have_pid = pid != 0 && pid != getpid();
 
         if (n_fds > 0 || have_pid) {
-                msghdr.msg_controllen = CMSG_SPACE(sizeof(int) * n_fds) +
-                                        CMSG_SPACE(sizeof(struct ucred) * have_pid);
+                /* CMSG_SPACE(0) may return value different then zero, which results in miscalculated controllen. */
+                msghdr.msg_controllen = (n_fds ? CMSG_SPACE(sizeof(int) * n_fds) : 0) +
+                                        CMSG_SPACE(sizeof(struct ucred)) * have_pid;
                 msghdr.msg_control = alloca(msghdr.msg_controllen);
 
                 cmsg = CMSG_FIRSTHDR(&msghdr);