librpc: fixed the GUID_compare() function

When comparing two unsigned values you can't just subtract
them.

Imagine you are comparing: "uint32_t u1" and "uint32_t u2". If you use
"u1 - u2" and u2 is zero, then the signed integer result will depend
on the top bit of u1.

This error occurs in a few places in Samba. For DRS replication it
resulted in corrupt uptodateness vectors.

1 files changed, 5 insertions, 5 deletions

diff --git a/librpc/ndr/uuid.c b/librpc/ndr/uuid.c
index 429a1b1ac9..1899afbbca 100644
--- a/librpc/ndr/uuid.c
+++ b/librpc/ndr/uuid.c
@@ -241,23 +241,23 @@ _PUBLIC_ bool GUID_equal(const struct GUID *u1, const struct GUID *u2)
 _PUBLIC_ int GUID_compare(const struct GUID *u1, const struct GUID *u2)
 {
 	if (u1->time_low != u2->time_low) {
-		return u1->time_low - u2->time_low;
+		return u1->time_low > u2->time_low ? 1 : -1;
 	}
 
 	if (u1->time_mid != u2->time_mid) {
-		return u1->time_mid - u2->time_mid;
+		return u1->time_mid > u2->time_mid ? 1 : -1;
 	}
 
 	if (u1->time_hi_and_version != u2->time_hi_and_version) {
-		return u1->time_hi_and_version - u2->time_hi_and_version;
+		return u1->time_hi_and_version > u2->time_hi_and_version ? 1 : -1;
 	}
 
 	if (u1->clock_seq[0] != u2->clock_seq[0]) {
-		return u1->clock_seq[0] - u2->clock_seq[0];
+		return u1->clock_seq[0] > u2->clock_seq[0] ? 1 : -1;
 	}
 
 	if (u1->clock_seq[1] != u2->clock_seq[1]) {
-		return u1->clock_seq[1] - u2->clock_seq[1];
+		return u1->clock_seq[1] > u2->clock_seq[1] ? 1 : -1;
 	}
 
 	return memcmp(u1->node, u2->node, 6);