From: ebiederm@xmission.com (Eric W. Biederman)
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Willy Tarreau <w@1wt.eu>, Al Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@amacapital.net>,
Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
Brad Spengler <spender@grsecurity.net>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] proc: make proc_fd_permission() thread-friendly
Date: Mon, 26 Aug 2013 12:10:16 -0700 [thread overview]
Message-ID: <8738pwp8tj.fsf@xmission.com> (raw)
In-Reply-To: <20130826184631.GA30917@redhat.com> (Oleg Nesterov's message of "Mon, 26 Aug 2013 20:46:31 +0200")
Oleg Nesterov <oleg@redhat.com> writes:
> On 08/26, Eric W. Biederman wrote:
>>
>> Oleg Nesterov <oleg@redhat.com> writes:
>>
>> > proc_fd_permission() says "process can still access /proc/self/fd
>> > after it has executed a setuid()", but the "task_pid() = proc_pid()
>> > check only helps if the task is group leader, /proc/self points to
>> > /proc/leader-pid.
>> >
>> > Change this check to use task_tgid() so that the whole process can
>> > access /proc/self/fd.
>>
>> There is at least a semantic goofiness here.
>>
>> There is /proc/<tgid>/fd and /proc/<tgid>/task/<pid>/fd, and the same
>> permission check is used by both.
>
> Yes, and we have /proc/<tid>/ which includes fd as well.
>
>> We might just want to have a /proc/thread symlink as well so people
>> don't have this issue.
>
> Yes! I agree.
>
> In particular, from the changelog:
>
> Note: CLONE_THREAD doesn't require CLONE_FILES so task->files can
> differ,
>
> so /proc/self/fd doesn't necessarily mean current->files, this can confuse
> the application.
>
> And I also assume that you agree with this change ;)
I don't disagree. Comparing tgid to pids is goofy and my brain is
elsewhere so I have no thought through the implications.
Actually thinking I think the check should really be. In which case we
are comparing what we really care about.
int proc_fd_permission(struct inode *inode, int mask)
{
int rv = generic_permission(inode, mask);
if (rv == 0)
return 0;
rcu_read_lock();
struct task *task = pid_task(proc_pid(inode));
if (task && (current->files == task->files))
rv = 0;
rcu_read_unlock();
return rv;
}
Eric
next prev parent reply other threads:[~2013-08-26 19:10 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-21 19:14 [PATCH v2] vfs: Tighten up linkat(..., AT_EMPTY_PATH) Andy Lutomirski
[not found] ` <CA+55aFxi-ps2f2M8xPhfbuQ0pToqupPrDsLi2+GPUK2sqdYfUw@mail.gmail.com>
[not found] ` <CALCETrW7+LcexA6v6RQDKhni_yJAduOmiSDneCpq3v8sPDvwUQ@mail.gmail.com>
2013-08-21 20:16 ` Willy Tarreau
2013-08-22 18:48 ` Linus Torvalds
2013-08-22 18:53 ` Willy Tarreau
2013-08-22 19:05 ` Andy Lutomirski
2013-08-22 19:23 ` Linus Torvalds
2013-08-22 20:10 ` Andy Lutomirski
2013-08-22 20:15 ` Willy Tarreau
2013-08-22 20:22 ` Andy Lutomirski
2013-08-22 20:44 ` Linus Torvalds
2013-08-22 20:48 ` Andy Lutomirski
2013-08-22 20:54 ` Linus Torvalds
2013-08-22 20:58 ` Andy Lutomirski
2013-08-23 1:07 ` Al Viro
2013-08-25 3:37 ` Al Viro
2013-08-25 7:26 ` Andy Lutomirski
2013-08-25 14:23 ` Al Viro
2013-08-25 17:04 ` Andy Lutomirski
2013-08-25 19:57 ` Linus Torvalds
2013-08-25 20:06 ` Al Viro
2013-08-25 20:23 ` Linus Torvalds
2013-08-26 17:37 ` Linus Torvalds
2013-08-26 18:07 ` Linus Torvalds
2013-08-26 18:11 ` Andy Lutomirski
2013-08-27 19:16 ` [RFC PATCH] fs: Add user_file_or_path_at and use it for truncate Andy Lutomirski
2013-08-27 19:32 ` Linus Torvalds
2013-08-27 20:28 ` Andy Lutomirski
2013-08-28 6:16 ` Al Viro
2013-08-28 16:24 ` Linus Torvalds
2013-08-28 19:04 ` Andy Lutomirski
2013-08-28 19:59 ` Al Viro
2013-08-28 21:07 ` Andy Lutomirski
2013-08-27 23:08 ` Al Viro
2013-08-27 23:13 ` Andy Lutomirski
2013-08-24 18:29 ` /proc/pid/fd && anon_inode_fops Oleg Nesterov
2013-08-24 21:24 ` Willy Tarreau
2013-08-25 5:23 ` Al Viro
2013-08-25 6:50 ` Willy Tarreau
2013-08-25 18:51 ` Linus Torvalds
2013-08-25 19:48 ` Oleg Nesterov
2013-08-25 20:05 ` Linus Torvalds
2013-08-26 15:33 ` Oleg Nesterov
2013-08-26 16:37 ` Oleg Nesterov
2013-08-26 17:54 ` [PATCH] proc: make proc_fd_permission() thread-friendly Oleg Nesterov
2013-08-26 18:09 ` Linus Torvalds
2013-08-26 19:35 ` Linus Torvalds
2013-08-26 20:20 ` Willy Tarreau
2013-08-27 15:05 ` Oleg Nesterov
2013-08-27 14:39 ` [PATCH 0/1] proc: make /proc/self point to thread Oleg Nesterov
2013-08-27 14:40 ` [PATCH 1/1] " Oleg Nesterov
2013-08-27 16:39 ` Linus Torvalds
2013-08-27 17:49 ` Oleg Nesterov
2013-08-27 18:15 ` Linus Torvalds
2013-08-27 18:28 ` Oleg Nesterov
[not found] ` <CALCETrXP-mYBPRon=0NzexW1FK1Qxz2+Bwv7-WeHBQpvW7ywRg@mail.gmail.com>
2013-08-27 15:45 ` [PATCH] proc: make proc_fd_permission() thread-friendly Oleg Nesterov
2013-08-26 18:32 ` Eric W. Biederman
2013-08-26 18:46 ` Oleg Nesterov
2013-08-26 18:56 ` Oleg Nesterov
2013-08-26 19:10 ` Eric W. Biederman [this message]
2013-08-27 14:53 ` Oleg Nesterov
2013-08-25 18:32 ` /proc/pid/fd && anon_inode_fops Linus Torvalds
2013-08-25 19:11 ` Al Viro
2013-08-25 19:17 ` Andy Lutomirski
2013-09-03 15:58 ` Pavel Machek
2013-08-25 15:45 ` Oleg Nesterov
2013-08-22 19:39 ` [PATCH v2] vfs: Tighten up linkat(..., AT_EMPTY_PATH) Willy Tarreau
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8738pwp8tj.fsf@xmission.com \
--to=ebiederm@xmission.com \
--cc=akpm@linux-foundation.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=spender@grsecurity.net \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
--cc=w@1wt.eu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).