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Subject[PATCH] exec: test ->recursion_depth
Test that trivially recursing script onto itself doesn't work.

Note: this is different test from ELOOP tests in execveat.c
Those test that execveat(2) doesn't follow symlinks when told to do so.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

tools/testing/selftests/exec/.gitignore | 3 -
tools/testing/selftests/exec/Makefile | 4 +
tools/testing/selftests/exec/recursion-depth.c | 67 +++++++++++++++++++++++++
3 files changed, 73 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/exec/.gitignore
+++ b/tools/testing/selftests/exec/.gitignore
@@ -6,4 +6,5 @@ execveat.moved
execveat.path.ephemeral
execveat.ephemeral
execveat.denatured
-xxxxxxxx*
\ No newline at end of file
+/recursion-depth
+xxxxxxxx*
--- a/tools/testing/selftests/exec/Makefile
+++ b/tools/testing/selftests/exec/Makefile
@@ -1,11 +1,15 @@
# SPDX-License-Identifier: GPL-2.0
CFLAGS = -Wall
+CFLAGS += -Wno-nonnull
+CFLAGS += -D_GNU_SOURCE

TEST_GEN_PROGS := execveat
TEST_GEN_FILES := execveat.symlink execveat.denatured script subdir
# Makefile is a run-time dependency, since it's accessed by the execveat test
TEST_FILES := Makefile

+TEST_GEN_PROGS += recursion-depth
+
EXTRA_CLEAN := $(OUTPUT)/subdir.moved $(OUTPUT)/execveat.moved $(OUTPUT)/xxxxx*

include ../lib.mk
new file mode 100644
--- /dev/null
+++ b/tools/testing/selftests/exec/recursion-depth.c
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2019 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/* Test that pointing #! script interpreter to self doesn't recurse. */
+#include <errno.h>
+#include <sched.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/mount.h>
+#include <unistd.h>
+
+int main(void)
+{
+ if (unshare(CLONE_NEWNS) == -1) {
+ if (errno == ENOSYS || errno == EPERM) {
+ fprintf(stderr, "error: unshare, errno %d\n", errno);
+ return 4;
+ }
+ fprintf(stderr, "error: unshare, errno %d\n", errno);
+ return 1;
+ }
+ if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) == -1) {
+ fprintf(stderr, "error: mount '/', errno %d\n", errno);
+ return 1;
+ }
+ /* Require "exec" filesystem. */
+ if (mount(NULL, "/tmp", "ramfs", 0, NULL) == -1) {
+ fprintf(stderr, "error: mount ramfs, errno %d\n", errno);
+ return 1;
+ }
+
+#define FILENAME "/tmp/1"
+
+ int fd = creat(FILENAME, 0700);
+ if (fd == -1) {
+ fprintf(stderr, "error: creat, errno %d\n", errno);
+ return 1;
+ }
+#define S "#!" FILENAME "\n"
+ if (write(fd, S, strlen(S)) != strlen(S)) {
+ fprintf(stderr, "error: write, errno %d\n", errno);
+ return 1;
+ }
+ close(fd);
+
+ int rv = execve(FILENAME, NULL, NULL);
+ if (rv == -1 && errno == ELOOP) {
+ return 0;
+ }
+ fprintf(stderr, "error: execve, rv %d, errno %d\n", rv, errno);
+ return 1;
+}
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