tools/libxs: Fix CLOEXEC handling in xs_fileno()

xs_fileno() opens a pipe on first use to communicate between the watch thread
and the main thread.  Nothing ever sets CLOEXEC on the file descriptors.

Check for the availability of the pipe2() function with configure.  Despite
starting life as Linux-only, FreeBSD and NetBSD have gained it.

When pipe2() isn't available, try our best with pipe() and set_cloexec().

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>

diff --git a/tools/config.h.in b/tools/config.h.in
index 0bb2fe08a143dcdb8e307b800b3861fad0a7fe08..50ad60fcb091d4a494b54103735e70db971ee228 100644 (file)
--- a/tools/config.h.in
+++ b/tools/config.h.in
@@ -39,6 +39,9 @@
 /* Define to 1 if you have the <memory.h> header file. */
 #undef HAVE_MEMORY_H
 
+/* Define to 1 if you have the `pipe2' function. */
+#undef HAVE_PIPE2
+
 /* pygrub enabled */
 #undef HAVE_PYGRUB
 

diff --git a/tools/configure b/tools/configure
index 459bfb56520e0267f4d9c7623baf4a697b3e0294..a6b43bfc606434f1ff088460d3abed34aa988152 100755 (executable)
--- a/tools/configure
+++ b/tools/configure
@@ -9751,6 +9751,18 @@ if test "$ax_found" = "0"; then :
 fi
 
 
+for ac_func in pipe2
+do :
+  ac_fn_c_check_func "$LINENO" "pipe2" "ac_cv_func_pipe2"
+if test "x$ac_cv_func_pipe2" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_PIPE2 1
+_ACEOF
+
+fi
+done
+
+
 cat >confcache <<\_ACEOF
 # This file is a shell script that caches the results of configure
 # tests run on this system so they can be shared between configure

diff --git a/tools/configure.ac b/tools/configure.ac
index 851887080c5e4813e0957cd6b8f2905ca468cc57..ac0fdc4314c4108201ac57c239d30e3a0f599cf5 100644 (file)
--- a/tools/configure.ac
+++ b/tools/configure.ac
@@ -543,4 +543,6 @@ AS_IF([test "x$pvshim" = "xy"], [
 
 AX_FIND_HEADER([INCLUDE_ENDIAN_H], [endian.h sys/endian.h])
 
+AC_CHECK_FUNCS([pipe2])
+
 AC_OUTPUT()

diff --git a/tools/libs/store/xs.c b/tools/libs/store/xs.c
index 11a766c508871154d5dd7ef475213e078c37b07b..c8845b69e2849e201a90569571a7f22084a76adb 100644 (file)
--- a/tools/libs/store/xs.c
+++ b/tools/libs/store/xs.c
@@ -190,13 +190,27 @@ static bool set_cloexec(int fd)
        return fcntl(fd, flags | FD_CLOEXEC) >= 0;
 }
 
+static int pipe_cloexec(int fds[2])
+{
+#if HAVE_PIPE2
+       return pipe2(fds, O_CLOEXEC);
+#else
+       if (pipe(fds) < 0)
+               return -1;
+       /* Best effort to set CLOEXEC.  Racy. */
+       set_cloexec(fds[0]);
+       set_cloexec(fds[1]);
+       return 0;
+#endif
+}
+
 int xs_fileno(struct xs_handle *h)
 {
        char c = 0;
 
        mutex_lock(&h->watch_mutex);
 
-       if ((h->watch_pipe[0] == -1) && (pipe(h->watch_pipe) != -1)) {
+       if ((h->watch_pipe[0] == -1) && (pipe_cloexec(h->watch_pipe) != -1)) {
                /* Kick things off if the watch list is already non-empty. */
                if (!XEN_TAILQ_EMPTY(&h->watch_list))
                        while (write(h->watch_pipe[1], &c, 1) != 1)