From: Al Viro <viro@ZenIV.linux.org.uk>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Joe Malicki <jmalicki@metacarta.com>,
Michael Itz <mitz@metacarta.com>,
Kenneth Baker <bakerk@metacarta.com>,
Chris Wright <chrisw@sous-sol.org>,
David Howells <dhowells@redhat.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
Greg Kroah-Hartman <gregkh@suse.de>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Q: check_unsafe_exec() races (Was: [PATCH 2/4] fix setuid sometimes doesn't)
Date: Sun, 29 Mar 2009 05:10:22 +0100 [thread overview]
Message-ID: <20090329041022.GF28946@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20090329005343.GA12139@redhat.com>
On Sun, Mar 29, 2009 at 01:53:43AM +0100, Oleg Nesterov wrote:
> Can't find the patch which introduced check_unsafe_exec(), so
> I am asking here.
>
> How it is supposed to work?
>
> Let's suppose we have two threads T1 and T2. T1 exits, and calls
> exit_fs().
>
> exit_fs:
>
> tsk->fs = NULL;
> // WINDOW
> put_fs_struct(fs);
>
> Now, if T2 does exec() and check_unsafe_exec() happens in the WINDOW
> above, we set LSM_UNSAFE_SHARE.
>
> Or we can race with sub-thread doing clone(CLONE_FS|CLONE_THREAD),
> the new thread is not visible in ->thread_group, buy copy_fs()
> can already increment fs->count.
Frankly, I don't think we really care. Note that having several sub-threads
and doing execve() in one of them will kill the rest, so you really want
to do some kind of synchronization to get something similar to reasonable
behaviour anyway.
> Another question. Why do we check sighand->count? We always unshare
> ->sighand on exec, see de_thread().
Correct. That check can and should go.
next prev parent reply other threads:[~2009-03-29 4:11 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-28 23:16 [PATCH 1/4] compat_do_execve should unshare_files Hugh Dickins
2009-03-28 23:20 ` [PATCH 2/4] fix setuid sometimes doesn't Hugh Dickins
2009-03-29 0:53 ` Q: check_unsafe_exec() races (Was: [PATCH 2/4] fix setuid sometimes doesn't) Oleg Nesterov
2009-03-29 4:10 ` Al Viro [this message]
2009-03-29 4:14 ` Al Viro
2009-03-29 4:52 ` Oleg Nesterov
2009-03-29 5:55 ` Al Viro
2009-03-29 6:01 ` Al Viro
2009-03-29 21:36 ` Oleg Nesterov
2009-03-29 22:20 ` Al Viro
2009-03-29 23:56 ` Oleg Nesterov
2009-03-30 0:03 ` Oleg Nesterov
2009-03-30 1:08 ` Al Viro
2009-03-30 1:13 ` Al Viro
2009-03-30 1:36 ` Oleg Nesterov
2009-03-30 1:40 ` Oleg Nesterov
2009-03-30 12:31 ` Al Viro
2009-03-30 14:32 ` Hugh Dickins
2009-03-31 6:16 ` Al Viro
2009-04-01 0:28 ` Hugh Dickins
2009-04-01 2:38 ` Al Viro
2009-04-01 3:03 ` Al Viro
2009-04-01 11:25 ` Hugh Dickins
2009-04-06 15:31 ` Oleg Nesterov
2009-04-19 16:30 ` Hugh Dickins
2009-04-21 16:10 ` Oleg Nesterov
2009-04-21 16:31 ` Linus Torvalds
2009-04-21 17:15 ` Oleg Nesterov
2009-04-21 17:35 ` Linus Torvalds
2009-04-21 19:39 ` Hugh Dickins
2009-04-23 23:01 ` [PATCH 1/2] do_execve() must not clear fs->in_exec if it was set by another thread Oleg Nesterov
2009-04-23 23:18 ` Roland McGrath
2009-04-23 23:31 ` Al Viro
2009-04-24 11:57 ` [PATCH 3/2] check_unsafe_exec: rcu_read_unlock Hugh Dickins
2009-04-24 14:34 ` Oleg Nesterov
2009-04-24 4:20 ` [PATCH 1/2] do_execve() must not clear fs->in_exec if it was set by another thread Hugh Dickins
2009-04-23 23:02 ` [PATCH 2/2] check_unsafe_exec: s/lock_task_sighand/rcu_read_lock/ Oleg Nesterov
2009-04-23 23:18 ` Roland McGrath
2009-04-24 4:29 ` Hugh Dickins
2009-04-01 11:18 ` Q: check_unsafe_exec() races (Was: [PATCH 2/4] fix setuid sometimes doesn't) Hugh Dickins
2009-04-06 15:51 ` Oleg Nesterov
2009-04-19 16:44 ` Hugh Dickins
2009-04-21 16:39 ` Oleg Nesterov
2009-03-30 23:45 ` Serge E. Hallyn
2009-03-31 6:19 ` Al Viro
2009-03-28 23:21 ` [PATCH 3/4] fix setuid sometimes wouldn't Hugh Dickins
2009-03-29 11:19 ` Alexey Dobriyan
2009-03-29 21:48 ` Oleg Nesterov
2009-03-29 22:37 ` Al Viro
2009-03-28 23:23 ` [PATCH 4/4] Annotate struct fs_struct's usage count restriction Hugh Dickins
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=20090329041022.GF28946@ZenIV.linux.org.uk \
--to=viro@zeniv.linux.org.uk \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=bakerk@metacarta.com \
--cc=chrisw@sous-sol.org \
--cc=dhowells@redhat.com \
--cc=gregkh@suse.de \
--cc=hugh@veritas.com \
--cc=jmalicki@metacarta.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mitz@metacarta.com \
--cc=oleg@redhat.com \
--cc=torvalds@linux-foundation.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.