From: Paul Moore <paul@paul-moore.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>,
"chengjian (D)" <cj.chengjian@huawei.com>,
neilb@suse.com, Anna.Schumaker@netapp.com, keescook@chromium.org,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
viro@zeniv.linux.org.uk,
"Xiexiuqi (Xie XiuQi)" <xiexiuqi@huawei.com>,
Li Bin <huawei.libin@huawei.com>,
yanaijie@huawei.com, peterz@infradead.org, mingo@redhat.com,
Linux Security Module list
<linux-security-module@vger.kernel.org>,
selinux@vger.kernel.org
Subject: Re: kernel BUG at kernel/cred.c:434!
Date: Mon, 15 Apr 2019 12:20:08 -0400 [thread overview]
Message-ID: <CAHC9VhSk1_fWooexHK0+5cKum55qTvj3uv5sRE=aJ4mv2GHJZg@mail.gmail.com> (raw)
In-Reply-To: <20190415150520.GA13257@redhat.com>
On Mon, Apr 15, 2019 at 11:05 AM Oleg Nesterov <oleg@redhat.com> wrote:
> On 04/15, Paul Moore wrote:
> >
> > On Mon, Apr 15, 2019 at 9:43 AM Oleg Nesterov <oleg@redhat.com> wrote:
> > > Well, acct("/proc/self/attr/current") doesn't look like a good idea, but I do
> > > not know where should we put the additional check... And probably
> > > "echo /proc/self/attr/current > /proc/sys/kernel/core_pattern" can hit the
> > > same problem, do_coredump() does override_creds() too.
> > >
> > > May be just add
> > >
> > > if (current->cred != current->real_cred)
> > > return -EACCES;
> > >
> > > into proc_pid_attr_write(), I dunno.
> >
> > Is the problem that do_acct_process() is calling override_creds() and
> > the returned/old credentials are being freed before do_acct_process()
> > can reinstall the creds via revert_creds()? Presumably because the
> > process accounting is causing the credentials to be replaced?
>
> Afaics, the problem is that do_acct_process() does override_creds() and
> then __kernel_write(). Which calls proc_pid_attr_write(), which in turn calls
> selinux_setprocattr(), which does another prepare_creds() + commit_creds();
> and commit_creds() hits
>
> BUG_ON(task->cred != old);
Gotcha. In the process of looking at the backtrace I forgot about the
BUG_ON() at the top of the oops message.
I wonder what terrible things would happen if we changed the BUG_ON()
in commit_creds to simple returning an error an error code to the
caller. There is a warning/requirement in commit_creds() function
header comment that it should always return 0.
--
paul moore
www.paul-moore.com
next prev parent reply other threads:[~2019-04-15 16:20 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <6e4428ca-3da1-a033-08f7-a51e57503989@huawei.com>
2019-04-12 15:28 ` kernel BUG at kernel/cred.c:434! Casey Schaufler
2019-04-15 13:43 ` Oleg Nesterov
2019-04-15 14:48 ` Paul Moore
2019-04-15 15:05 ` Oleg Nesterov
2019-04-15 16:20 ` Paul Moore [this message]
2019-04-16 3:40 ` Kees Cook
2019-04-16 14:46 ` chengjian (D)
2019-04-17 14:30 ` Paul Moore
2019-04-17 14:57 ` Oleg Nesterov
2019-04-17 15:39 ` Casey Schaufler
2019-04-17 15:40 ` Paul Moore
2019-04-17 16:27 ` Oleg Nesterov
2019-04-17 16:42 ` Casey Schaufler
2019-04-18 13:39 ` Stephen Smalley
2019-04-17 23:39 ` Paul Moore
2019-04-18 0:17 ` John Johansen
2019-04-18 0:24 ` Casey Schaufler
2019-04-18 2:49 ` Yang Yingliang
2019-04-19 2:04 ` Paul Moore
2019-04-19 2:34 ` Yang Yingliang
2019-04-19 13:24 ` Paul Moore
2019-04-19 14:34 ` Yang Yingliang
2019-04-19 16:13 ` Paul Moore
2019-04-20 7:38 ` Yang Yingliang
2019-04-22 19:48 ` Paul Moore
2019-04-23 4:08 ` Yang Yingliang
2019-04-23 20:18 ` Paul Moore
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='CAHC9VhSk1_fWooexHK0+5cKum55qTvj3uv5sRE=aJ4mv2GHJZg@mail.gmail.com' \
--to=paul@paul-moore.com \
--cc=Anna.Schumaker@netapp.com \
--cc=casey@schaufler-ca.com \
--cc=cj.chengjian@huawei.com \
--cc=huawei.libin@huawei.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=neilb@suse.com \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=selinux@vger.kernel.org \
--cc=viro@zeniv.linux.org.uk \
--cc=xiexiuqi@huawei.com \
--cc=yanaijie@huawei.com \
/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).