From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Pádraig Brady" <P@draigBrady.com>
Cc: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
avagin@openvz.org, "Ludovic Courtès" <ludo@gnu.org>
Subject: Re: query re unlink() ... inotify ... open() race
Date: Sat, 12 Sep 2015 02:14:51 +0100 [thread overview]
Message-ID: <20150912011449.GP22011@ZenIV.linux.org.uk> (raw)
In-Reply-To: <55F371AB.20805@draigBrady.com>
On Sat, Sep 12, 2015 at 01:28:27AM +0100, Pádraig Brady wrote:
> The open() succeeding is surprising. Is that allowed?
> The summary of the sequence in the kernel is:
>
> vfs_unlink() {
> mutex_lock(&(dentry->d_inode->i_mutex));
> security_inode_unlink(dir, dentry);
> try_break_deleg(target, delegated_inode);
> dir->i_op->unlink(dir, dentry);
> dont_mount(dentry);
> detach_mounts(dentry);
> mutex_unlock(&(dentry->d_inode->i_mutex));
>
> fsnotify_link_count(target)
> d_delete(dentry);
> }
... and ->unlink() is the one to decrement the link count. With lookup
via dcache coming at some point after that. idiotify is a red herring
here - stat(2) will report decremented link count just as well.
prev parent reply other threads:[~2015-09-12 1:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-12 0:28 query re unlink() ... inotify ... open() race Pádraig Brady
2015-09-12 1:14 ` Al Viro [this message]
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