From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Vincent Minet <v.minet@criteo.com>
Cc: linux-kernel@vger.kernel.org,
Luis Chamberlain <mcgrof@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] umh: fix memory leak on execve failure
Date: Tue, 14 Apr 2020 07:56:42 +0900 [thread overview]
Message-ID: <a4cd5557-2466-7826-bf82-5d91ff96a13c@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20200413154925.GA18663@criteo.com>
Hello.
On 2020/04/14 0:49, Vincent Minet wrote:
> In my case, execve fails with ENOENT on a Tomoyo enabled kernel. It doesn't seem
> like CONFIG_BPFILTER and CONFIG_SECURITY_TOMOYO are compatible as it is.
Thanks for the report. Yes, I know this is a potential problem since 3.19 and
this is a practical problem since 4.18, as explained at
https://lkml.kernel.org/r/f8099e95-c0fc-d133-471e-e0ba97d2230e@i-love.sakura.ne.jp .
>
> The UMH is executed via "do_execve_file", so we'll have bprm->filename set to
> "none". This causes the following call chain to fail and search_binary_handler()
> to return ENOENT.
> search_binary_handler() ->
> security_bprm_check() ->
> tomoyo_bprm_check_security() ->
> tomoyo_find_next_domain() ->
> tomoyo_realpath_nofollow()
>
> I don't really know how to solve this. As I understand it, you really need
> a "valid" pathname for Tomoyo and it's not obvious what that should be for the
> user-mode blob.
It seems that Al wants to change __do_execve_file(), as commented at
https://lkml.kernel.org/r/20200329031702.GB23230@ZenIV.linux.org.uk .
Bringing tomoyo_realpath_nofollow() to __do_execve_file() (in other words,
solve AT_SYMLINK_NOFOLLOW path and !AT_SYMLINK_NOFOLLOW path at the same
time) will be the right (from the perspective of race-free) solution. But
I don't know an API that allows resolving !AT_SYMLINK_NOFOLLOW path starting
from AT_SYMLINK_NOFOLLOW path. I need to wait for Al, for I can't implement
race-free solution from TOMOYO side.
next prev parent reply other threads:[~2020-04-13 22:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-13 15:42 [PATCH] umh: fix memory leak on execve failure Vincent Minet
2020-04-13 15:49 ` Vincent Minet
2020-04-13 22:56 ` Tetsuo Handa [this message]
2020-05-07 22:14 Vincent Minet
2020-05-09 2:10 ` Jakub Kicinski
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