udf: fix possible leakage of blocks

We have to take care that when we call udf_discard_prealloc() from
udf_clear_inode() we have to write inode ourselves afterwards (otherwise,
some changes might be lost leading to leakage of blocks, use of free blocks
or improperly aligned extents).

Also udf_discard_prealloc() does two different things - it removes
preallocated blocks and truncates the last extent to exactly match i_size.
We move the latter functionality to udf_truncate_tail_extent(), call
udf_discard_prealloc() when last reference to a file is dropped and call
udf_truncate_tail_extent() when inode is being removed from inode cache
(udf_clear_inode() call).

We cannot call udf_truncate_tail_extent() earlier as subsequent open+write
would find the last block of the file mapped and happily write to the end
of it, although the last extent says it's shorter.

[akpm@linux-foundation.org: Make checkpatch.pl happier]
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Eric Sandeen <sandeen@sandeen.net>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 1f0129405cf..bf7de0bdbab 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -100,14 +100,23 @@ no_delete:
 	clear_inode(inode);
 }
 
+/*
+ * If we are going to release inode from memory, we discard preallocation and
+ * truncate last inode extent to proper length. We could use drop_inode() but
+ * it's called under inode_lock and thus we cannot mark inode dirty there.  We
+ * use clear_inode() but we have to make sure to write inode as it's not written
+ * automatically.
+ */
 void udf_clear_inode(struct inode *inode)
 {
 	if (!(inode->i_sb->s_flags & MS_RDONLY)) {
 		lock_kernel();
+		/* Discard preallocation for directories, symlinks, etc. */
 		udf_discard_prealloc(inode);
+		udf_truncate_tail_extent(inode);
 		unlock_kernel();
+		write_inode_now(inode, 1);
 	}
-
 	kfree(UDF_I_DATA(inode));
 	UDF_I_DATA(inode) = NULL;
 }