From: Denys Vlasenko <dvlasenk@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>,
Eric Dumazet <edumazet@google.com>,
Jan Kratochvil <jan.kratochvil@redhat.com>,
Julien Tinnes <jln@google.com>, Kees Cook <keescook@google.com>,
Kostya Serebryany <kcc@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
Pedro Alves <palves@redhat.com>,
Robert Swiecki <swiecki@google.com>,
Roland McGrath <roland@hack.frob.com>,
syzkaller@googlegroups.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] wait/ptrace: always assume __WALL if the child is traced
Date: Thu, 22 Oct 2015 15:51:35 +0200 [thread overview]
Message-ID: <5628E9E7.4020500@redhat.com> (raw)
In-Reply-To: <20151020171754.GA29304@redhat.com>
On 10/20/2015 07:17 PM, Oleg Nesterov wrote:
> creates the unreapable zombie if /sbin/init doesn't use __WALL.
>
> This is not a kernel bug, at least in a sense that everything works as
> expected: debugger should reap a traced sub-thread before it can reap
> the leader, but without __WALL/__WCLONE do_wait() ignores sub-threads.
>
> Unfortunately, it seems that /sbin/init in most (all?) distributions
> doesn't use it and we have to change the kernel to avoid the problem.
>
> This patch just adds the "ptrace" check into eligible_child(). To some
> degree this matches the "tsk->ptrace" in exit_notify(), ->exit_signal
> is mostly ignored when the tracee reports to debugger.
>
> This obviously means the user-visible change: __WCLONE and __WALL no
> longer have any meaning for debugger. And I can only hope that this
> won't break something.
>
> We could make a more conservative change. Say, we can take __WCLONE
> into account, or !thread_group_leader(). But it would be nice to not
> complicate these historical/confusing checks.
For the record, I like this way of fixing the problem too.
It removes the need to ever use __WALL in userspace:
IIRC the only case where it was needed are debuggers.
Which in turn makes *all* underscored wait flags (__WCLONE, __WALL,
__WNOTHREAD) unnecessary for any sane application use.
next prev parent reply other threads:[~2015-10-22 13:51 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-20 17:17 [PATCH 0/2] wait/ptrace: always assume __WALL if the child is traced Oleg Nesterov
2015-10-20 17:17 ` [PATCH 1/2] " Oleg Nesterov
2015-10-20 22:31 ` Andrew Morton
2015-10-21 3:27 ` Vasily Averin
2015-10-21 17:41 ` Oleg Nesterov
2015-10-21 19:47 ` Andrew Morton
2015-10-21 20:44 ` Oleg Nesterov
2015-10-21 19:59 ` Denys Vlasenko
2015-10-21 20:31 ` Denys Vlasenko
2015-10-21 21:47 ` Oleg Nesterov
2015-10-21 23:27 ` Denys Vlasenko
2015-10-25 15:54 ` Oleg Nesterov
2015-10-26 12:08 ` Pedro Alves
2015-10-28 16:11 ` Oleg Nesterov
2015-10-28 15:43 ` Pedro Alves
2015-10-28 19:02 ` Oleg Nesterov
2015-10-22 13:51 ` Denys Vlasenko [this message]
2015-10-20 17:17 ` [PATCH 2/2] wait: allow sys_waitid() to use __WNOTHREAD/__WCLONE/__WALL Oleg Nesterov
2015-10-20 17:36 ` [PATCH 0/2] wait/ptrace: always assume __WALL if the child is traced Oleg Nesterov
2015-10-22 14:40 ` Pedro Alves
2015-10-25 15:42 ` Oleg Nesterov
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=5628E9E7.4020500@redhat.com \
--to=dvlasenk@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=dvyukov@google.com \
--cc=edumazet@google.com \
--cc=glider@google.com \
--cc=jan.kratochvil@redhat.com \
--cc=jln@google.com \
--cc=kcc@google.com \
--cc=keescook@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mtk.manpages@gmail.com \
--cc=oleg@redhat.com \
--cc=palves@redhat.com \
--cc=roland@hack.frob.com \
--cc=swiecki@google.com \
--cc=syzkaller@googlegroups.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 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).