From d96002942cf66e04bd332e266bf18399224ebe91 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Wed, 7 Apr 2021 09:18:56 +1000
Subject: [PATCH] AP_Filesystem: ensure all blocks are filled on upload

---
 .../AP_Filesystem/AP_Filesystem_Mission.cpp   | 20 +++++++++++++++++++
 .../AP_Filesystem/AP_Filesystem_Mission.h     |  3 +++
 2 files changed, 23 insertions(+)

diff --git a/libraries/AP_Filesystem/AP_Filesystem_Mission.cpp b/libraries/AP_Filesystem/AP_Filesystem_Mission.cpp
index 1f3d60c3b0..3084ad9684 100644
--- a/libraries/AP_Filesystem/AP_Filesystem_Mission.cpp
+++ b/libraries/AP_Filesystem/AP_Filesystem_Mission.cpp
@@ -320,6 +320,17 @@ int32_t AP_Filesystem_Mission::write(int fd, const void *buf, uint32_t count)
     return count;
 }
 
+// see if a block of memory is all zero
+bool AP_Filesystem_Mission::all_zero(const uint8_t *b, uint8_t len) const
+{
+    while (len--) {
+        if (*b++ != 0) {
+            return false;
+        }
+    }
+    return true;
+}
+
 /*
   finish mission upload
  */
@@ -342,6 +353,15 @@ bool AP_Filesystem_Mission::finish_upload(const rfile &r)
         return false;
     }
 
+    // if any item is all zeros then reject, it means client didn't
+    // fill in the whole file
+    for (uint32_t i=0; i<nitems; i++) {
+        const uint8_t *b2 = b + sizeof(hdr) + i*item_size;
+        if (all_zero(b2, item_size)) {
+            return false;
+        }
+    }
+
     auto *mission = AP::mission();
     if (mission == nullptr) {
         return false;
diff --git a/libraries/AP_Filesystem/AP_Filesystem_Mission.h b/libraries/AP_Filesystem/AP_Filesystem_Mission.h
index 142bb75a5a..0f9d75bd39 100644
--- a/libraries/AP_Filesystem/AP_Filesystem_Mission.h
+++ b/libraries/AP_Filesystem/AP_Filesystem_Mission.h
@@ -62,4 +62,7 @@ private:
 
     // finish loading items
     bool finish_upload(const rfile &r);
+
+    // see if a block of memory is all zero
+    bool all_zero(const uint8_t *b, uint8_t size) const;
 };