[PATCH] uml: fix off-by-one bug in VM file creation

Fix an off-by-one bug in temp file creation.  Seeking to the desired length
and writing a byte resulted in the file being one byte longer than expected.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index d24d1a9..560c806 100644 (file)
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -210,8 +210,11 @@ int create_tmp_file(unsigned long long len)
                exit(1);
        }
 
-        if (lseek64(fd, len, SEEK_SET) < 0) {
-               perror("os_seek_file");
+       /* Seek to len - 1 because writing a character there will
+        * increase the file size by one byte, to the desired length.
+        */
+       if (lseek64(fd, len - 1, SEEK_SET) < 0) {
+               perror("os_seek_file");
                exit(1);
        }