ash: fix open fds leaking in redirects. Closes 9561

commit e19923f665 deleted clearredir()
call in shellexec():

	ash: [REDIR] Remove redundant CLOEXEC calls
	Upstream commit:

	Now that we're marking file descriptors as CLOEXEC in savefd, we no longer
	need to close them on exec or in setinputfd.

but it missed one place where we don't set CLOEXEC. Fixing this.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash.c

@@ -5426,11 +5426,11 @@ redirect(union node *redir, int flags)
 			/* Careful to not accidentally "save"
 			 * to the same fd as right side fd in N>&M */
 			int minfd = right_fd < 10 ? 10 : right_fd + 1;
+#if defined(F_DUPFD_CLOEXEC)
+			i = fcntl(fd, F_DUPFD_CLOEXEC, minfd);
+#else
 			i = fcntl(fd, F_DUPFD, minfd);
-/* You'd expect copy to be CLOEXECed. Currently these extra "saved" fds
- * are closed in popredir() in the child, preventing them from leaking
- * into child. (popredir() also cleans up the mess in case of failures)
- */
+#endif
 			if (i == -1) {
 				i = errno;
 				if (i != EBADF) {
@@ -5445,6 +5445,9 @@ redirect(union node *redir, int flags)
  remember_to_close:
 				i = CLOSED;
 			} else { /* fd is open, save its copy */
+#if !defined(F_DUPFD_CLOEXEC)
+				fcntl(i, F_SETFD, FD_CLOEXEC);
+#endif
 				/* "exec fd>&-" should not close fds
 				 * which point to script file(s).
 				 * Force them to be restored afterwards */

shell/ash_test/ash-redir/redir_leak.right

@@ -0,0 +1,6 @@
+4
+4
+4
+4
+4
+4

shell/ash_test/ash-redir/redir_leak.tests

@@ -0,0 +1,10 @@
+# Each of these should show only four lines:
+# fds 0,1,2 are stdio; fd 3 is open by opendir() in ls.
+# This test detects bugs where redirects leave stray open fds.
+
+ls -1 /proc/self/fd | wc -l
+ls -1 /proc/self/fd >/proc/self/fd/1 | wc -l
+ls -1 /proc/self/fd >/proc/self/fd/1 2>&1 | wc -l
+echo "`ls -1 /proc/self/fd `" | wc -l
+echo "`ls -1 /proc/self/fd >/proc/self/fd/1 `" | wc -l
+echo "`ls -1 /proc/self/fd >/proc/self/fd/1 2>&1 `" | wc -l

shell/hush_test/hush-redir/redir_leak.right

@@ -0,0 +1,6 @@
+4
+4
+4
+4
+4
+4

shell/hush_test/hush-redir/redir_leak.tests

@@ -0,0 +1,10 @@
+# Each of these should show only four lines:
+# fds 0,1,2 are stdio; fd 3 is open by opendir() in ls.
+# This test detects bugs where redirects leave stray open fds.
+
+ls -1 /proc/self/fd | wc -l
+ls -1 /proc/self/fd >/proc/self/fd/1 | wc -l
+ls -1 /proc/self/fd >/proc/self/fd/1 2>&1 | wc -l
+echo "`ls -1 /proc/self/fd `" | wc -l
+echo "`ls -1 /proc/self/fd >/proc/self/fd/1 `" | wc -l
+echo "`ls -1 /proc/self/fd >/proc/self/fd/1 2>&1 `" | wc -l