Fixed minor UAF bug. Added makefile

.gitignore

@@ -53,3 +53,5 @@ dkms.conf
 
 # Output build artifacts
 bin/
+test.c
+mathtest

Makefile

@@ -0,0 +1,13 @@
+clean:
+	rm -f $(wildcard *.o)
+	rm -f $(wildcard *.so)
+
+build: varint.c
+	gcc -Wall -c -O3 -fPIC varint.c
+	gcc -o libCMath.so -shared varint.o
+
+rebuild: clean build
+test: test.c clean build
+	rm -f a.out
+	gcc -Wall -o mathtest -L$(shell pwd) test.c -lCMath
+	./mathtest

varint.c

@@ -47,12 +47,14 @@ unsigned long long varint_decode(varint varint){
             return header;
     }
     if(header <= 248){
-            free(varint);
+            unsigned long long result = 240UL + ((header - 241) << 8) + (unsigned char)varint[1];
-            return 240UL + ((header - 241) << 8) + (unsigned char)varint[1];
+            free(varint); 
+            return result;       
     }
     if(header == 249){
+            unsigned long long result = 2288UL + ((unsigned char)varint[1] << 8) + (unsigned char)varint[2];
             free(varint);
-            return 2288UL + ((unsigned char)varint[1] << 8) + (unsigned char)varint[2];
+            return result;
     }
     unsigned long result = (unsigned char)varint[1] | ((unsigned char)varint[2] << 8) | ((unsigned char)varint[3]);
     int compare = 2;