From: Francois-Xavier Le Bail <devel.fx.lebail@orange.fr>
Date: Sun, 17 Mar 2019 14:01:15 +0000 (+0100)
Subject: CDP: Fix two loops for undefined behavior at runtime
X-Git-Tag: tcpdump-4.99-bp~901
X-Git-Url: https://git.tcpdump.org/tcpdump/commitdiff_plain/6c93708db1cd314ab4e6511596c625d617a15853

CDP: Fix two loops for undefined behavior at runtime

The errors were:
print-cdp.c:363:13: runtime error: unsigned integer overflow: 0 - 1
cannot be represented in type 'u_int' (aka 'unsigned int')
print-cdp.c:375:13: runtime error: unsigned integer overflow: 0 - 1
cannot be represented in type 'u_int' (aka 'unsigned int')
---

diff --git a/print-cdp.c b/print-cdp.c
index 79d7046c..e63ce911 100644
--- a/print-cdp.c
+++ b/print-cdp.c
@@ -360,9 +360,10 @@ cdp_print_addr(netdissect_options *ndo,
 			if (p + pl > endp)
 				goto trunc;
 			ND_PRINT("pt=0x%02x, pl=%u, pb=", EXTRACT_U_1((p - 2)), pl);
-			while (pl-- > 0) {
+			while (pl != 0) {
 				ND_PRINT(" %02x", EXTRACT_U_1(p));
 				p++;
+				pl--;
 			}
 			ND_TCHECK_2(p);
 			if (p + 2 > endp)
@@ -372,9 +373,10 @@ cdp_print_addr(netdissect_options *ndo,
 			ND_TCHECK_LEN(p, al);
 			if (p + al > endp)
 				goto trunc;
-			while (al-- > 0) {
+			while (al != 0) {
 				ND_PRINT(" %02x", EXTRACT_U_1(p));
 				p++;
+				al--;
 			}
 		}
 		num--;