From: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Date: Sat, 5 Sep 2015 13:20:15 +0000 (+0200)
Subject: sd-daemon: fix sd_is_mq for non-mq fds
X-Git-Tag: v227.2^2~46
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=9277945f9aca8ed56f8575ab3c6bab5ace859d3a;p=elogind.git

sd-daemon: fix sd_is_mq for non-mq fds

mq_getattr returns -1/EBADF for file descriptors which are not mq.
But we should return 0 in this case.

We first check that fd is a valid fd, so we can assume that if
mq_getattr returns EBADF, it is simply a non-mq fd. There is a slight
race, but there doesn't seem to be a nice way to fix it.
---

diff --git a/src/libelogind/sd-daemon/sd-daemon.c b/src/libelogind/sd-daemon/sd-daemon.c
index af3dab7e4..7639b6d3b 100644
--- a/src/libelogind/sd-daemon/sd-daemon.c
+++ b/src/libelogind/sd-daemon/sd-daemon.c
@@ -315,10 +315,15 @@ _public_ int sd_is_socket_unix(int fd, int type, int listening, const char *path
 _public_ int sd_is_mq(int fd, const char *path) {
         struct mq_attr attr;
 
-        assert_return(fd >= 0, -EBADF);
+        /* Check that the fd is valid */
+        assert_return(fcntl(fd, F_GETFD) >= 0, -errno);
 
-        if (mq_getattr(fd, &attr) < 0)
+        if (mq_getattr(fd, &attr) < 0) {
+                if (errno == EBADF)
+                        /* A non-mq fd (or an invalid one, but we ruled that out above) */
+                        return 0;
                 return -errno;
+        }
 
         if (path) {
                 char fpath[PATH_MAX];