libext2fs: Potential null ptr deref in undo_err_handler_init

In the !undo_io_backing_manager case, undo_err_handler_init
will be passed a null data->real, which will be dereferenced.

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

diff --git a/lib/ext2fs/undo_io.c b/lib/ext2fs/undo_io.c
index 454f3b6..da1cf45 100644 (file)
--- a/lib/ext2fs/undo_io.c
+++ b/lib/ext2fs/undo_io.c
@@ -400,7 +400,8 @@ static errcode_t undo_open(const char *name, int flags, io_channel *channel)
         * setup err handler for read so that we know
         * when the backing manager fails do short read
         */
-       undo_err_handler_init(data->real);
+       if (data->real)
+               undo_err_handler_init(data->real);
 
        *channel = io;
        return 0;