resize2fs: Add sanity check for off_t overflow before truncating

If we can't use ftruncate64(), and have to use ftruncate() instead,
make sure that we don't accidentally truncate the size when we chop it
down to an off_t before calling ftruncate(), lest we severely damage a
filesystem image file.

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

diff --git a/resize/main.c b/resize/main.c
index 7db4ebc..b3f80f7 100644 (file)
--- a/resize/main.c
+++ b/resize/main.c
@@ -416,7 +416,9 @@ int main (int argc, char ** argv)
 #ifdef HAVE_FSTAT64
                ftruncate64(fd, new_file_size);
 #else
-               ftruncate(fd, (off_t) new_file_size);
+               /* Only truncate if new_file_size doesn't overflow off_t */
+               if (((off_t) new_file_size) == new_file_size)
+                       ftruncate(fd, (off_t) new_file_size);
 #endif
        }
        if (fd > 0)