From 2a542af8829c4fa938556dbf404fcf21fefbf91d Mon Sep 17 00:00:00 2001
From: William Pitcock <nenolod@dereferenced.org>
Date: Wed, 7 Feb 2018 20:21:57 -0600
Subject: loader: gracefully handle user-exec of the ELF interpreter itself

---
 loader/loader.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/loader/loader.c b/loader/loader.c
index 53a2c38..ebcdbfe 100644
--- a/loader/loader.c
+++ b/loader/loader.c
@@ -34,6 +34,12 @@
 #error LOADER must be defined
 #endif
 
+void usage(void)
+{
+	printf("This is the gcompat ELF interpreter stub.\n");
+	printf("You are not meant to run this directly.\n");
+}
+
 /*
  * Given the argv { "foo", "bar", "baz" }, and the environment variable
  * "LD_PRELOAD=/another/preload.so", the new argv will be {
@@ -96,6 +102,12 @@ int main(int argc, char *argv[], char *envp[])
 	}
 	target[len] = '\0';
 
+	/* somebody is trying to run the loader directly */
+	if (strstr(target, LOADER) != NULL) {
+		usage();
+		return EXIT_FAILURE;
+	}
+
 	new_argv[0] = LOADER;
 	new_argv[1] = "--argv0";
 	new_argv[2] = argv[0];
-- 
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