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

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Message-ID: <20130826163704.GA21763@redhat.com>
Date:	Mon, 26 Aug 2013 18:37:04 +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

On 08/26, Oleg Nesterov wrote:
>
> Not sure we really want this in this case but
>
> 	$ ./ls /proc/self/fd
> 	0  1  2  3
>
> still works, I guess thanks to proc_fd_permission().

And btw. Whatever we do, shouldn't we change proc_fd_permission()?

/proc/self is actually /proc/tgid, this means that the task_pid()
check can't help if a sub-thread uses /proc/self.

Oleg.

--- x/fs/proc/fd.c
+++ x/fs/proc/fd.c
@@ -288,7 +288,7 @@ int proc_fd_permission(struct inode *ino
 	int rv = generic_permission(inode, mask);
 	if (rv == 0)
 		return 0;
-	if (task_pid(current) == proc_pid(inode))
+	if (task_tgid(current) == proc_pid(inode))
 		rv = 0;
 	return rv;
 }

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