X-Git-Url: https://git.octo.it/?p=rrdtool.git;a=blobdiff_plain;f=src%2Frrd_open.c;h=c6a2d7d9d49f09a65eaa01f263e23975c97a4064;hp=0774bced2996703eb5b80d4ee7dab9ba343b68ff;hb=f972da18c85ebeb8591f585e7480fae9c1c5c380;hpb=24ebf1bad3d26067cd34cf5cb62d7c936ec2baf7

diff --git a/src/rrd_open.c b/src/rrd_open.c
index 0774bce..c6a2d7d 100644
--- a/src/rrd_open.c
+++ b/src/rrd_open.c
@@ -440,8 +440,13 @@ inline ssize_t rrd_read(
 {
 #ifdef HAVE_MMAP
     size_t    _cnt = count;
-    ssize_t   _surplus = rrd_file->pos + _cnt - rrd_file->file_len;
+    ssize_t   _surplus;
 
+    if (rrd_file->pos > rrd_file->file_len || _cnt == 0) /* EOF */
+       return 0;
+    if (buf == NULL)
+       return -1; /* EINVAL */
+    _surplus = rrd_file->pos + _cnt - rrd_file->file_len;
     if (_surplus > 0) { /* short read */
         _cnt -= _surplus;
     }