selftests/bpf: Sanitize pointer prior fclose()

There are scenarios where env.{sub,}test_state->stdout_saved, can be
NULL, e.g. sometimes when the watchdog timeout kicks in, or if the
open_memstream syscall is not available.

Avoid crashing test_progs by adding an explicit NULL check prior the
fclose() call.

Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20250318081648.122523-1-bjorn@kernel.org

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index d4ec9586b98caff33cba470691668386fbcd7981..309d9d4a8ace1dcad44642e5a6a110af69cc3e7d 100644 (file)
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -103,12 +103,14 @@ static void stdio_restore(void)
        pthread_mutex_lock(&stdout_lock);
 
        if (env.subtest_state) {
-               fclose(env.subtest_state->stdout_saved);
+               if (env.subtest_state->stdout_saved)
+                       fclose(env.subtest_state->stdout_saved);
                env.subtest_state->stdout_saved = NULL;
                stdout = env.test_state->stdout_saved;
                stderr = env.test_state->stdout_saved;
        } else {
-               fclose(env.test_state->stdout_saved);
+               if (env.test_state->stdout_saved)
+                       fclose(env.test_state->stdout_saved);
                env.test_state->stdout_saved = NULL;
                stdout = env.stdout_saved;
                stderr = env.stderr_saved;