Fix chunk start problem properly

[yaffs2.git] / yaffs_guts.c

diff --git a/yaffs_guts.c b/yaffs_guts.c
index 40d534585ba6082f3cf8ba5a8b1cac10b888eafa..ae6e342502f40d585a39a47f74e771016316b95c 100644 (file)
--- a/yaffs_guts.c
+++ b/yaffs_guts.c
@@ -12,7 +12,7 @@
  */
 
 const char *yaffs_guts_c_version =
-    "$Id: yaffs_guts.c,v 1.69 2009-01-04 21:44:23 charles Exp $";
+    "$Id: yaffs_guts.c,v 1.70 2009-01-09 02:52:28 charles Exp $";
 
 #include "yportenv.h"
 
@@ -4847,7 +4847,8 @@ int yaffs_WriteDataToFile(yaffs_Object * in, const __u8 * buffer, loff_t offset,
         int nToWriteBack;
         int startOfWrite = offset;
         int chunkWritten = 0;
-        int nBytesRead;
+        __u32 nBytesRead;
+        __u32 chunkStart;
 
        yaffs_Device *dev;
 
@@ -4877,9 +4878,12 @@ int yaffs_WriteDataToFile(yaffs_Object * in, const __u8 * buffer, loff_t offset,
                         * we need to write back as much as was there before.
                         */
 
-                       nBytesRead =
-                           in->variant.fileVariant.fileSize -
-                           ((chunk - 1) * dev->nDataBytesPerChunk);
+                       chunkStart = ((chunk - 1) * dev->nDataBytesPerChunk);
+
+                       if(chunkStart > in->variant.fileVariant.fileSize)
+                               nBytesRead = 0; /* Past end of file */
+                       else
+                               nBytesRead = in->variant.fileVariant.fileSize - chunkStart;
 
                        if (nBytesRead > dev->nDataBytesPerChunk) {
                                nBytesRead = dev->nDataBytesPerChunk;
@@ -4887,7 +4891,10 @@ int yaffs_WriteDataToFile(yaffs_Object * in, const __u8 * buffer, loff_t offset,
 
                        nToWriteBack =
                            (nBytesRead >
-                            ((int)start + n)) ? nBytesRead : (start + n);
+                            (start + n)) ? nBytesRead : (start + n);
+                       
+                       if(nToWriteBack < 0 || nToWriteBack > dev->nDataBytesPerChunk)
+                               YBUG();
 
                } else {
                        nToCopy = dev->nDataBytesPerChunk - start;