linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: James Morris <jmorris@namei.org>
To: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	syzbot <syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com>,
	syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH] Yama: Check for pid death before checking ancestry
Date: Thu, 17 Jan 2019 07:02:34 +1100 (AEDT)	[thread overview]
Message-ID: <alpine.LRH.2.21.1901170702280.2986@namei.org> (raw)
In-Reply-To: <20190116183109.GA21722@beast>

On Wed, 16 Jan 2019, Kees Cook wrote:

> It's possible that a pid has died before we take the rcu lock, in which
> case we can't walk the ancestry list as it may be detached. Instead, check
> for death first before doing the walk.
> 
> Reported-by: syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com
> Fixes: 2d514487faf1 ("security: Yama LSM")
> Cc: stable@vger.kernel.org
> Suggested-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> James, can you please send this to Linus in your -fixes tree?

Done.

> ---
>  security/yama/yama_lsm.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> index ffda91a4a1aa..02514fe558b4 100644
> --- a/security/yama/yama_lsm.c
> +++ b/security/yama/yama_lsm.c
> @@ -368,7 +368,9 @@ static int yama_ptrace_access_check(struct task_struct *child,
>  			break;
>  		case YAMA_SCOPE_RELATIONAL:
>  			rcu_read_lock();
> -			if (!task_is_descendant(current, child) &&
> +			if (!pid_alive(child))
> +				rc = -EPERM;
> +			if (!rc && !task_is_descendant(current, child) &&
>  			    !ptracer_exception_found(current, child) &&
>  			    !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
>  				rc = -EPERM;
> 

-- 
James Morris
<jmorris@namei.org>


  reply	other threads:[~2019-01-16 20:03 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-16 18:31 Kees Cook
2019-01-16 20:02 ` James Morris [this message]
2019-01-16 20:02   ` James Morris

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=alpine.LRH.2.21.1901170702280.2986@namei.org \
    --to=jmorris@namei.org \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=oleg@redhat.com \
    --cc=penguin-kernel@i-love.sakura.ne.jp \
    --cc=serge@hallyn.com \
    --cc=syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com \
    --cc=syzkaller-bugs@googlegroups.com \
    --subject='Re: [PATCH] Yama: Check for pid death before checking ancestry' \
    /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

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).