fsx: Add check for mmap last-page zero fill

Check to make sure the VM system provided 0's beyond the true end of
the file mapping (as required by mmap def in 1996 posix 1003.1)

This check was taken from the FreeBSD version of fsx.c.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/ltp/fsx.c b/ltp/fsx.c
index 6ebc0c6b0f2201af6dff82a3c4f1cb6699bd50c0..e4c528dfb9ed2182da3ce980bf88968dbf31122a 100644 (file)
--- a/ltp/fsx.c
+++ b/ltp/fsx.c
@@ -9,6 +9,8 @@
  *     Rewritten 8/98 by Conrad Minshall.
  *
  *     Small changes to work under Linux -- davej.
+ *
+ *     Checks for mmap last-page zero fill.
  */
 
 #include "global.h"
@@ -503,6 +505,33 @@ doread(unsigned offset, unsigned size)
 }
 
 
+void
+check_eofpage(char *s, unsigned offset, char *p, int size)
+{
+       unsigned long last_page, should_be_zero;
+
+       if (offset + size <= (file_size & ~page_mask))
+               return;
+       /*
+        * we landed in the last page of the file
+        * test to make sure the VM system provided 0's 
+        * beyond the true end of the file mapping
+        * (as required by mmap def in 1996 posix 1003.1)
+        */
+       last_page = ((unsigned long)p + (offset & page_mask) + size) & ~page_mask;
+
+       for (should_be_zero = last_page + (file_size & page_mask);
+            should_be_zero < last_page + page_size;
+            should_be_zero++)
+               if (*(char *)should_be_zero) {
+                       prt("Mapped %s: non-zero data past EOF (0x%llx) page offset 0x%x is 0x%04x\n",
+                           s, file_size - 1, should_be_zero & page_mask,
+                           short_at(should_be_zero));
+                       report_failure(205);
+               }
+}
+
+
 void
 domapread(unsigned offset, unsigned size)
 {
@@ -547,6 +576,9 @@ domapread(unsigned offset, unsigned size)
                report_failure(190);
        }
        memcpy(temp_buf, p + pg_offset, size);
+
+       check_eofpage("Read", offset, p, size);
+
        if (munmap(p, map_size) != 0) {
                prterr("domapread: munmap");
                report_failure(191);
@@ -696,6 +728,9 @@ domapwrite(unsigned offset, unsigned size)
                prterr("domapwrite: msync");
                report_failure(203);
        }
+
+       check_eofpage("Write", offset, p, size);
+
        if (munmap(p, map_size) != 0) {
                prterr("domapwrite: munmap");
                report_failure(204);