linux-kernel - Re: /proc/pid/fd && anon_inode

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Message-ID: <20130825194844.GA16717@redhat.com>
Date:	Sun, 25 Aug 2013 21:48:44 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Willy Tarreau <w@....eu>, Al Viro <viro@...iv.linux.org.uk>,
	Andy Lutomirski <luto@...capital.net>,
	"security@...nel.org" <security@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Brad Spengler <spender@...ecurity.net>
Subject: Re: /proc/pid/fd && anon_inode_fops

Cough. I am going off-topic again, but I can't resist...

On 08/25, Linus Torvalds wrote:
>
> Look at the code that creates the fd stat information, for example.
> It's in tid_fd_revalidate(), and it really doesn't make much sense to
> use the task credentials for it.

Or pid_revalidate(), but my concern is task_dumpable() logic.

pid_revalidate() does inode->i_*id = GLOBAL_ROOT_*ID if task_dumpable()
fails, but it can fail simply because ->mm = NULL.

This means that almost everything in /proc/zombie-pid/ becomes root.
Doesn't really hurt, but for what? Looks a bit strange imho.

Oleg.

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