Hi!
> From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
>
> commit e72b9dd6a5f17d0fb51f16f8685f3004361e83d0 upstream.
>
> lower_dentry can't go from positive to negative (we have it pinned),
> but it *can* go from negative to positive. So fetching ->d_inode
> into a local variable, doing a blocking allocation, checking that
> now ->d_inode is non-NULL and feeding the value we'd fetched
> earlier to a function that won't accept NULL is not a good idea.
>
> Cc: stable@xxxxxxxxxxxxxxx
> --- a/fs/ecryptfs/inode.c
> +++ b/fs/ecryptfs/inode.c
> @@ -345,7 +345,15 @@ static struct dentry *ecryptfs_lookup_in
> dentry_info->lower_path.mnt = lower_mnt;
> dentry_info->lower_path.dentry = lower_dentry;
>
> - if (d_really_is_negative(lower_dentry)) {
> + /*
> + * negative dentry can go positive under us here - its parent is not
> + * locked. That's OK and that could happen just as we return from
> + * ecryptfs_lookup() anyway. Just need to be careful and fetch
> + * ->d_inode only once - it's not stable here.
> + */
> + lower_inode = READ_ONCE(lower_dentry->d_inode);
Should this use d_inode_rcu() function, to keep the abstraction
provided by the header file?
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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