Index: cddl/contrib/opensolaris/lib/libdtrace/common/dt_printf.c
===================================================================
--- cddl/contrib/opensolaris/lib/libdtrace/common/dt_printf.c	(revision 285796)
+++ cddl/contrib/opensolaris/lib/libdtrace/common/dt_printf.c	(working copy)
@@ -1348,6 +1348,7 @@
 	dtrace_aggdesc_t *agg;
 	caddr_t lim = (caddr_t)buf + len, limit;
 	char format[64] = "%";
+	size_t ret;
 	int i, aggrec, curagg = -1;
 	uint64_t normal;
 
@@ -1380,6 +1381,7 @@
 		int rval;
 
 		char *f = format + 1; /* skip initial '%' */
+		size_t fmtsz = sizeof (format) -1;
 		const dtrace_recdesc_t *rec;
 		dt_pfprint_f *func;
 		caddr_t addr;
@@ -1558,11 +1560,17 @@
 		if (func == pfprint_stack && (pfd->pfd_flags & DT_PFCONV_LEFT))
 			width = 0;
 
-		if (width != 0)
-			f += snprintf(f, sizeof (format), "%d", ABS(width));
+		if (width != 0) {
+			ret = snprintf(f, fmtsz, "%d", ABS(width));
+			f += ret;
+			fmtsz = MAX(0, fmtsz - ret);
+		}
 
-		if (prec > 0)
-			f += snprintf(f, sizeof (format), ".%d", prec);
+		if (prec > 0) {
+			ret = snprintf(f, fmtsz, ".%d", prec);
+			f += ret;
+			fmtsz = MAX(0, fmtsz - ret);
+		}
 
 		(void) strcpy(f, pfd->pfd_fmt);
 		pfd->pfd_rec = rec;