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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 07:02:51 +1100 (AEDT)	[thread overview]
Message-ID: <alpine.LRH.2.21.1901170702420.2986@namei.org> (raw)
In-Reply-To: <alpine.LRH.2.21.1901170702280.2986@namei.org>

On Thu, 17 Jan 2019, James Morris wrote:

> 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.

I mean, queued in that tree.

> 
> > ---
> >  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
2019-01-16 20:02   ` James Morris [this message]

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