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Date:   Mon, 14 Jun 2021 08:32:35 -0700
From:   Kees Cook <keescook@chromium.org>
To:     youling257 <youling257@gmail.com>
Cc:     torvalds@linux-foundation.org, christian.brauner@ubuntu.com,
        andrea.righi@canonical.com, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org, regressions@lists.linux.dev,
        linux-security-module@vger.kernel.org,
        Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <stephen.smalley.work@gmail.com>,
        SElinux list <selinux@vger.kernel.org>
Subject: Re: [PATCH] proc: Track /proc/$pid/attr/ opener mm_struct
Message-ID: <202106140826.7912F27CD@keescook>
References: <20210608171221.276899-1-keescook@chromium.org>
 <20210614100234.12077-1-youling257@gmail.com>
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On Mon, Jun 14, 2021 at 06:02:34PM +0800, youling257 wrote:
> I used mainline kernel on android, this patch cause "failed to retrieve pid context" problem.
> 
> 06-14 02:15:51.165  1685  1685 E ServiceManager: SELinux: getpidcon(pid=1682) failed to retrieve pid context.
> 06-14 02:15:51.166  1685  1685 E ServiceManager: add_service('batteryproperties',1) uid=0 - PERMISSION DENIED
> 06-14 02:15:51.166  1682  1682 I ServiceManager: addService() batteryproperties failed (err -1 - no service manager yet?).  Retrying...
> 06-14 02:15:51.197  1685  1685 E ServiceManager: SELinux: getpidcon(pid=1695) failed to retrieve pid context.
> 06-14 02:15:51.197  1685  1685 E ServiceManager: add_service('android.security.keystore',1) uid=1017 - PERMISSION DENIED
> 06-14 02:15:51.198  1695  1695 I ServiceManager: addService() android.security.keystore failed (err -1 - no service manager yet?).  Retrying...
> 06-14 02:15:51.207  1685  1685 E ServiceManager: SELinux: getpidcon(pid=1708) failed to retrieve pid context.
> 06-14 02:15:51.207  1685  1685 E ServiceManager: add_service('android.service.gatekeeper.IGateKeeperService',1) uid=1000 - PERMISSION DENIED
> 06-14 02:15:51.207  1708  1708 I ServiceManager: addService() android.service.gatekeeper.IGateKeeperService failed (err -1 - no service manager yet?).  Retrying...
> 06-14 02:15:51.275  1685  1685 E ServiceManager: SELinux: getpidcon(pid=1693) failed to retrieve pid context.
> 06-14 02:15:51.275  1692  1692 I cameraserver: ServiceManager: 0xf6d309e0
> 06-14 02:15:51.275  1685  1685 E ServiceManager: add_service('drm.drmManager',1) uid=1019 - PERMISSION DENIED
> 06-14 02:15:51.276  1693  1693 I ServiceManager: addService() drm.drmManager failed (err -1 - no service manager yet?).  Retrying...
> 

Argh. Are you able to uncover what userspace is doing here?

So far, my test cases are:

1) self: open, write, close: allowed
2) self: open, clone thread. thread: change privileges, write, close: allowed
3) self: open, give to privileged process. privileged process: write: reject


-- 
Kees Cook