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-rw-r--r--contrib/tcpdump/interface.h12
1 files changed, 10 insertions, 2 deletions
diff --git a/contrib/tcpdump/interface.h b/contrib/tcpdump/interface.h
index 2459764d7b69..af069cb2f2dc 100644
--- a/contrib/tcpdump/interface.h
+++ b/contrib/tcpdump/interface.h
@@ -132,8 +132,16 @@ extern int snaplen;
extern const u_char *packetp;
extern const u_char *snapend;
-/* True if "l" bytes of "var" were captured */
-#define TTEST2(var, l) ((u_char *)&(var) <= snapend - (l))
+/*
+ * True if "l" bytes of "var" were captured.
+ *
+ * The "snapend - (l) <= snapend" checks to make sure "l" isn't so large
+ * that "snapend - (l)" underflows.
+ *
+ * The check is for <= rather than < because "l" might be 0.
+ */
+#define TTEST2(var, l) (snapend - (l) <= snapend && \
+ (const u_char *)&(var) <= snapend - (l))
/* True if "var" was captured */
#define TTEST(var) TTEST2(var, sizeof(var))