From 19550f9f7f63d6fe2dab191f2044f4e4f5d59df6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Joakim=20Nohlg=C3=A5rd?= <joakim.nohlgard@eistec.se>
Date: Sat, 23 Apr 2016 10:03:09 +0200
Subject: [PATCH] core/cfs: Disallow seeking past the end of a file if it is
 not writable

---
 core/cfs/cfs-coffee.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/core/cfs/cfs-coffee.c b/core/cfs/cfs-coffee.c
index 79eb18d94..37b1a707e 100644
--- a/core/cfs/cfs-coffee.c
+++ b/core/cfs/cfs-coffee.c
@@ -1055,7 +1055,12 @@ cfs_seek(int fd, cfs_offset_t offset, int whence)
   }
 
   if(fdp->file->end < new_offset) {
-    fdp->file->end = new_offset;
+    if(FD_WRITABLE(fd)) {
+      fdp->file->end = new_offset;
+    } else {
+      /* Disallow seeking past the end of the file for read only FDs */
+      return (cfs_offset_t)-1;
+    }
   }
 
   return fdp->offset = new_offset;