Change ownership of pid file, to keep systemd happy.

debian/changelog

@@ -5,7 +5,13 @@ dnsmasq (2.79-1) unstable; urgency=low
    * Fix exit code for dhcp_release6 (closes: #833596)
    * Add project homepage to control file. (closes: #887764)
 
- -- Simon Kelley <simon@thekelleys.org.uk>  Sat, 20 Jan 2018 22:17:01 +0000
+ -- Simon Kelley <simon@thekelleys.org.uk>  Tue, 6 Feb 2018 17:23:21 +0000
+
+dnsmasq (2.78-2) unstable; urgency=high
+
+   * Change ownership of pid file, to keep systemd happy. (closes: #889336)
+
+ -- Simon Kelley <simon@thekelleys.org.uk>  Tue, 6 Feb 2018 17:21:30 +0000
 
 dnsmasq (2.78-1) unstable; urgency=high
 

src/dnsmasq.c

@@ -541,7 +541,14 @@ int main (int argc, char **argv)
 	    }
 	  else
 	    {
-	      if (!read_write(fd, (unsigned char *)daemon->namebuff, strlen(daemon->namebuff), 0))
+	      /* We're still running as root here. Change the ownership of the PID file
+		 to the user we will be running as. Note that this is not to allow
+		 us to delete the file, since that depends on the permissions 
+		 of the directory containing the file. That directory will
+		 need to by owned by the dnsmasq user, and the ownership of the
+		 file has to match, to keep systemd >273 happy. */
+	      if ((getuid() == 0 && ent_pw && ent_pw->pw_uid != 0 && fchown(fd, ent_pw->pw_uid, ent_pw->pw_gid) == -1) ||
+		  !read_write(fd, (unsigned char *)daemon->namebuff, strlen(daemon->namebuff), 0))
 		err = 1;
 	      else
 		{