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Date:   Tue, 5 Jan 2021 17:45:31 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Stephen Brennan <stephen.s.brennan@oracle.com>
Cc:     Alexey Dobriyan <adobriyan@gmail.com>,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        linux-security-module@vger.kernel.org,
        Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <stephen.smalley.work@gmail.com>,
        Eric Paris <eparis@parisplace.org>, selinux@vger.kernel.org,
        Casey Schaufler <casey@schaufler-ca.com>,
        Eric Biederman <ebiederm@xmission.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v4] proc: Allow pid_revalidate() during LOOKUP_RCU
Message-ID: <20210105174531.GW3579531@ZenIV.linux.org.uk>
References: <20210104232123.31378-1-stephen.s.brennan@oracle.com>
 <20210105055935.GT3579531@ZenIV.linux.org.uk>
 <20210105165005.GV3579531@ZenIV.linux.org.uk>
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Sender: Al Viro <viro@ftp.linux.org.uk>
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On Tue, Jan 05, 2021 at 04:50:05PM +0000, Al Viro wrote:

> struct dentry *d_find_alias_rcu(struct inode *inode)
> {
> 	struct hlist_head *l = &inode->i_dentry;
>         struct dentry *de = NULL;
> 
> 	spin_lock(&inode->i_lock);
> 	// ->i_dentry and ->i_rcu are colocated, but the latter won't be
> 	// used without having I_FREEING set, which means no aliases left
> 	if (inode->i_state & I_FREEING) {
> 		spin_unlock(&inode->i_lock);
> 		return NULL;
> 	}
> 	// we can safely access inode->i_dentry
>         if (hlist_empty(p)) {

	if (hlist_empty(l)) {

obviously...