diff --git a/lib/doc/bin/docproc.c b/lib/doc/bin/docproc.c
index 74b3cdb..0719cdd 100644
--- a/lib/doc/bin/docproc.c
+++ b/lib/doc/bin/docproc.c
@@ -402,7 +402,8 @@ static void find_all_symbols(char *filename)
 			do {
 				while ((ret = read(pipefd[0],
 						   data + data_len,
-						   4096)) > 0) {
+						   4096)) > 0 &&
+				       data_len <= SIZE_MAX - 4096 - ret) {
 					data_len += (size_t)ret;
 					data = realloc(data, data_len + 4096);
 					if (!data) {