From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [PATCH 09/13] VFS/namei: enable RCU-walk when following symlinks.
Date: Mon, 16 Mar 2015 22:44:28 +0000
Message-ID: <20150316224428.GF29656@ZenIV.linux.org.uk>
References: <20150316043602.23648.52734.stgit@notabene.brown>
 <20150316044320.23648.43776.stgit@notabene.brown>
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Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
To: NeilBrown <neilb@suse.de>
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On Mon, Mar 16, 2015 at 03:43:20PM +1100, NeilBrown wrote:
>  	if (should_follow_link(path->dentry, follow)) {
> -		if (nd->flags & LOOKUP_RCU) {
> -			if (unlikely(unlazy_walk(nd, path->dentry))) {
> -				err = -ECHILD;
> -				goto out_err;
> -			}
> -		}
>  		BUG_ON(inode != path->dentry->d_inode);

... and now this BUG_ON() can bloody well be triggered.
>  	if (should_follow_link(path->dentry, !symlink_ok)) {
> -		if (nd->flags & LOOKUP_RCU) {
> -			if (unlikely(unlazy_walk(nd, path->dentry))) {
> -				error = -ECHILD;
> -				goto out;
> -			}
> -		}
>  		BUG_ON(inode != path->dentry->d_inode);

So can this.