libc: Fix t_spawn_fileactions test after ATF update

Since https://github.com/freebsd/atf/commit/4581cefc1e3811dd3c926b5dd4b15fd63d2e19da
ATF opens the results file on startup. This fixes problems like
capsicumized tests not being able to open the file on exit.

However, this test closes all file descriptors above 3 to get a
deterministic fd table allocation for the child. Instead of using closefrom
(which will close the ATF output file FD) I've changed this test use
the lowest available fd and pass that to the helper program as a string.

We could also try to re-open the results file in ATF if we get a EBADF
error, but that will fail when running under Capsicum.

Reviewed By:	cem
Differential Revision: https://reviews.freebsd.org/D28684

(cherry picked from commit 2aa3ef285a23d802f0bd6c7281612e16834e9b68)

2 files changed, 45 insertions, 24 deletions

diff --git a/contrib/netbsd-tests/lib/libc/gen/posix_spawn/h_fileactions.c b/contrib/netbsd-tests/lib/libc/gen/posix_spawn/h_fileactions.c
index d92337074481..fd7fb21ad6f5 100644
--- a/contrib/netbsd-tests/lib/libc/gen/posix_spawn/h_fileactions.c
+++ b/contrib/netbsd-tests/lib/libc/gen/posix_spawn/h_fileactions.c
@@ -49,48 +49,61 @@ int
 main(int argc, char **argv)
 {
 	int res = EXIT_SUCCESS;
+	long lowfd;
 	char buf[BUFSIZE];
 	struct stat sb0, sb1;
 
+	if (argc < 2) {
+		fprintf(stderr, "%s: Not enough arguments: %d\n", getprogname(),
+		    argc);
+		return EXIT_FAILURE;
+	}
+	lowfd = strtol(argv[1], NULL, 10);
+	if (lowfd < 3) {
+		fprintf(stderr, "%s: Invalid lowfd %d (as str: %s) \n",
+		    getprogname(), argc, argv[1]);
+		return EXIT_FAILURE;
+	}
+
 	strcpy(buf, "test...");
-	/* file desc 3 should be closed via addclose */
-	if (read(3, buf, BUFSIZE) != -1 || errno != EBADF) {
-		fprintf(stderr, "%s: filedesc 3 is not closed\n",
+	/* First fd should be closed via addclose */
+	if (read(lowfd, buf, BUFSIZE) != -1 || errno != EBADF) {
+		fprintf(stderr, "%s: first filedesc is not closed\n",
 		    getprogname());
 		res = EXIT_FAILURE;
 	}
-	/* file desc 4 should be closed via closeonexec */
-	if (read(4, buf, BUFSIZE) != -1 || errno != EBADF) {
-		fprintf(stderr, "%s: filedesc 4 is not closed\n",
+	/* Next file desc should be closed via closeonexec */
+	if (read(lowfd + 1, buf, BUFSIZE) != -1 || errno != EBADF) {
+		fprintf(stderr, "%s: filedesc +1 is not closed\n",
 		    getprogname());
 		res = EXIT_FAILURE;
 	}
-	/* file desc 5 remains open */
-	if (write(5, buf, BUFSIZE) <= 0) {
-		fprintf(stderr, "%s: could not write to filedesc 5\n",
+	/* file desc + 2 remains open */
+	if (write(lowfd + 2, buf, BUFSIZE) <= 0) {
+		fprintf(stderr, "%s: could not write to filedesc +2\n",
 		    getprogname());
 		res = EXIT_FAILURE;
 	}
-	/* file desc 6 should be open (via addopen) */
-	if (write(6, buf, BUFSIZE) <= 0) {
-		fprintf(stderr, "%s: could not write to filedesc 6\n",
+	/* file desc + 3 should be open (via addopen) */
+	if (write(lowfd + 3, buf, BUFSIZE) <= 0) {
+		fprintf(stderr, "%s: could not write to filedesc +3\n",
 		    getprogname());
 		res = EXIT_FAILURE;
 	}
-	/* file desc 7 should refer to stdout */
+	/* file desc + 4 should refer to stdout */
 	fflush(stdout);
 	if (fstat(fileno(stdout), &sb0) != 0) {
 		fprintf(stderr, "%s: could not fstat stdout\n",
 		    getprogname());
 		res = EXIT_FAILURE;
 	}
-	if (fstat(7, &sb1) != 0) {
-		fprintf(stderr, "%s: could not fstat filedesc 7\n",
+	if (fstat(lowfd + 4, &sb1) != 0) {
+		fprintf(stderr, "%s: could not fstat filedesc +4\n",
 		    getprogname());
 		res = EXIT_FAILURE;
 	}
-	if (write(7, buf, strlen(buf)) <= 0) {
-		fprintf(stderr, "%s: could not write to filedesc 7\n",
+	if (write(lowfd + 4, buf, strlen(buf)) <= 0) {
+		fprintf(stderr, "%s: could not write to filedesc +4\n",
 		    getprogname());
 		res = EXIT_FAILURE;
 	}
diff --git a/contrib/netbsd-tests/lib/libc/gen/posix_spawn/t_fileactions.c b/contrib/netbsd-tests/lib/libc/gen/posix_spawn/t_fileactions.c
index 74009a805758..b3d364207fbb 100644
--- a/contrib/netbsd-tests/lib/libc/gen/posix_spawn/t_fileactions.c
+++ b/contrib/netbsd-tests/lib/libc/gen/posix_spawn/t_fileactions.c
@@ -301,26 +301,34 @@ ATF_TC_BODY(t_spawn_fileactions, tc)
 {
 	int fd1, fd2, fd3, status, err;
 	pid_t pid;
-	char * const args[2] = { __UNCONST("h_fileactions"), NULL };
+	char *args[3] = { __UNCONST("h_fileactions"), NULL, NULL };
+	int lowfd;
+	char lowfdstr[32];
 	char helper[FILENAME_MAX];
 	posix_spawn_file_actions_t fa;
 
 	posix_spawn_file_actions_init(&fa);
 
-	closefrom(fileno(stderr)+1);
+	/* Note: this assumes no gaps in the fd table */
+	lowfd = open("/", O_RDONLY);
+	ATF_REQUIRE(lowfd > 0);
+	ATF_REQUIRE_EQ(0, close(lowfd));
+	snprintf(lowfdstr, sizeof(lowfdstr), "%d", lowfd);
+	args[1] = lowfdstr;
 
 	fd1 = open("/dev/null", O_RDONLY);
-	ATF_REQUIRE(fd1 == 3);
+	ATF_REQUIRE_EQ(fd1, lowfd);
 
 	fd2 = open("/dev/null", O_WRONLY, O_CLOEXEC);
-	ATF_REQUIRE(fd2 == 4);
+	ATF_REQUIRE_EQ(fd2, lowfd + 1);
 
 	fd3 = open("/dev/null", O_WRONLY);
-	ATF_REQUIRE(fd3 == 5);
+	ATF_REQUIRE_EQ(fd3, lowfd + 2);
 
 	posix_spawn_file_actions_addclose(&fa, fd1);
-	posix_spawn_file_actions_addopen(&fa, 6, "/dev/null", O_RDWR, 0);
-	posix_spawn_file_actions_adddup2(&fa, 1, 7); 
+	posix_spawn_file_actions_addopen(&fa, lowfd + 3, "/dev/null", O_RDWR,
+	    0);
+	posix_spawn_file_actions_adddup2(&fa, 1, lowfd + 4);
 
 	snprintf(helper, sizeof helper, "%s/h_fileactions",
 	    atf_tc_get_config_var(tc, "srcdir"));