tests: add a rudimentary fuzzer for server_process_syslog_message (#9979)

src/fuzz/fuzz-journald-syslog.c

@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "alloc-util.h"
+#include "fuzz.h"
+#include "journald-server.h"
+#include "journald-syslog.h"
+#include "sd-event.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+        Server s = {};
+        char *label = NULL;
+        size_t label_len = 0;
+        struct ucred *ucred = NULL;
+        struct timeval *tv = NULL;
+
+        if (size == 0)
+                return 0;
+
+        assert_se(sd_event_default(&s.event) >= 0);
+        s.syslog_fd = s.native_fd = s.stdout_fd = s.dev_kmsg_fd = s.audit_fd = s.hostname_fd = s.notify_fd = -1;
+        s.buffer = memdup_suffix0(data, size);
+        assert_se(s.buffer);
+        s.buffer_size = size + 1;
+        s.storage = STORAGE_NONE;
+        server_process_syslog_message(&s, s.buffer, size, ucred, tv, label, label_len);
+        server_done(&s);
+
+        return 0;
+}

src/fuzz/meson.build

@@ -19,6 +19,11 @@ fuzzers += [
           libshared],
          [libmount]],
 
+        [['src/fuzz/fuzz-journald-syslog.c'],
+         [libjournal_core,
+          libshared],
+         [libselinux]],
+
         [['src/fuzz/fuzz-journal-remote.c'],
          [libsystemd_journal_remote,
           libshared],