ext4: fix data corruption in data=journal mode

commit 3b136499e906460919f0d21a49db1aaccf0ae963 upstream.

ext4_journalled_write_end() did not propely handle all the cases when
generic_perform_write() did not copy all the data into the target page
and could mark buffers with uninitialized contents as uptodate and dirty
leading to possible data corruption (which would be quickly fixed by
generic_perform_write() retrying the write but still). Fix the problem
by carefully handling the case when the page that is written to is not
uptodate.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 10690e5ba2ebd2007de251866036b65931aa2650..88ae0aaa49d16f3a73b447a825ac04758d3d5340 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1220,7 +1220,9 @@ errout:
  * set the buffer to be dirty, since in data=journalled mode we need
  * to call ext4_handle_dirty_metadata() instead.
  */
-static void zero_new_buffers(struct page *page, unsigned from, unsigned to)
+static void ext4_journalled_zero_new_buffers(handle_t *handle,
+                                           struct page *page,
+                                           unsigned from, unsigned to)
 {
        unsigned int block_start = 0, block_end;
        struct buffer_head *head, *bh;
@@ -1237,7 +1239,7 @@ static void zero_new_buffers(struct page *page, unsigned from, unsigned to)
                                        size = min(to, block_end) - start;
 
                                        zero_user(page, start, size);
-                                       set_buffer_uptodate(bh);
+                                       write_end_fn(handle, bh);
                                }
                                clear_buffer_new(bh);
                        }
@@ -1269,15 +1271,16 @@ static int ext4_journalled_write_end(struct file *file,
        if (ext4_has_inline_data(inode))
                copied = ext4_write_inline_data_end(inode, pos, len,
                                                    copied, page);
-       else {
-               if (copied < len) {
-                       if (!PageUptodate(page))
-                               copied = 0;
-                       zero_new_buffers(page, from+copied, to);
-               }
-
+       else if (unlikely(copied < len) && !PageUptodate(page)) {
+               copied = 0;
+               ext4_journalled_zero_new_buffers(handle, page, from, to);
+       } else {
+               if (unlikely(copied < len))
+                       ext4_journalled_zero_new_buffers(handle, page,
+                                                        from + copied, to);
                ret = ext4_walk_page_buffers(handle, page_buffers(page), from,
-                                            to, &partial, write_end_fn);
+                                            from + copied, &partial,
+                                            write_end_fn);
                if (!partial)
                        SetPageUptodate(page);
        }