selftests/exec: Test for empty string on NULL argv

Test for the NULL argv argument producing a single empty string on exec.

Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/lkml/20220201011637.2457646-1-keescook@chromium.org

diff --git a/tools/testing/selftests/exec/Makefile b/tools/testing/selftests/exec/Makefile
index 12c5e27..551affb 100644 (file)
--- a/tools/testing/selftests/exec/Makefile
+++ b/tools/testing/selftests/exec/Makefile
@@ -10,6 +10,7 @@ TEST_GEN_FILES := execveat.symlink execveat.denatured script subdir
 TEST_FILES := Makefile
 
 TEST_GEN_PROGS += recursion-depth
+TEST_GEN_PROGS += null-argv
 
 EXTRA_CLEAN := $(OUTPUT)/subdir.moved $(OUTPUT)/execveat.moved $(OUTPUT)/xxxxx*        \
               $(OUTPUT)/S_I*.test

diff --git a/tools/testing/selftests/exec/null-argv.c b/tools/testing/selftests/exec/null-argv.c
new file mode 100644 (file)
index 0000000..c19726e
--- /dev/null
+++ b/tools/testing/selftests/exec/null-argv.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Test that empty argvs are swapped out for a single empty string. */
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "../kselftest.h"
+
+#define FORK(exec)                             \
+do {                                           \
+       pid = fork();                           \
+       if (pid == 0) {                         \
+               /* Child */                     \
+               exec; /* Some kind of exec */   \
+               perror("# " #exec);             \
+               return 1;                       \
+       }                                       \
+       check_result(pid, #exec);               \
+} while (0)
+
+void check_result(pid_t pid, const char *msg)
+{
+       int wstatus;
+
+       if (pid == (pid_t)-1) {
+               perror("# fork");
+               ksft_test_result_fail("fork failed: %s\n", msg);
+               return;
+       }
+       if (waitpid(pid, &wstatus, 0) < 0) {
+               perror("# waitpid");
+               ksft_test_result_fail("waitpid failed: %s\n", msg);
+               return;
+       }
+       if (!WIFEXITED(wstatus)) {
+               ksft_test_result_fail("child did not exit: %s\n", msg);
+               return;
+       }
+       if (WEXITSTATUS(wstatus) != 0) {
+               ksft_test_result_fail("non-zero exit: %s\n", msg);
+               return;
+       }
+       ksft_test_result_pass("%s\n", msg);
+}
+
+int main(int argc, char *argv[], char *envp[])
+{
+       pid_t pid;
+       static char * const args[] = { NULL };
+       static char * const str[] = { "", NULL };
+
+       /* argc counting checks */
+       if (argc < 1) {
+               fprintf(stderr, "# FAIL: saw argc == 0 (old kernel?)\n");
+               return 1;
+       }
+       if (argc != 1) {
+               fprintf(stderr, "# FAIL: unknown argc (%d)\n", argc);
+               return 1;
+       }
+       if (argv[0][0] == '\0') {
+               /* Good, we found a NULL terminated string at argv[0]! */
+               return 0;
+       }
+
+       /* Test runner. */
+       ksft_print_header();
+       ksft_set_plan(5);
+
+       FORK(execve(argv[0], str, NULL));
+       FORK(execve(argv[0], NULL, NULL));
+       FORK(execve(argv[0], NULL, envp));
+       FORK(execve(argv[0], args, NULL));
+       FORK(execve(argv[0], args, envp));
+
+       ksft_exit(ksft_cnt.ksft_pass == ksft_plan);
+}