From: Bernd Edlinger <bernd.edlinger@hotmail.de>
To: Christian Brauner <christian.brauner@ubuntu.com>,
Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Thomas Gleixner <tglx@linutronix.de>,
Oleg Nesterov <oleg@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>,
Andrei Vagin <avagin@gmail.com>, Ingo Molnar <mingo@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Yuyang Du <duyuyang@gmail.com>,
David Hildenbrand <david@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Anshuman Khandual <anshuman.khandual@arm.com>,
David Howells <dhowells@redhat.com>,
James Morris <jamorris@linux.microsoft.com>,
Kees Cook <keescook@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Shakeel Butt <shakeelb@google.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Christian Kellner <christian@kellner.me>,
Andrea Arcangeli <aarcange@redhat.com>,
Aleksa Sarai <cyphar@cyphar.com>,
"Dmitry V. Levin" <ldv@altlinux.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH] exec: Fix a deadlock in ptrace
Date: Sun, 1 Mar 2020 19:00:24 +0000 [thread overview]
Message-ID: <AM6PR03MB51702321B8A0E6A8C41ED3D5E4E60@AM6PR03MB5170.eurprd03.prod.outlook.com> (raw)
In-Reply-To: <20200301185244.zkofjus6xtgkx4s3@wittgenstein>
On 3/1/20 7:52 PM, Christian Brauner wrote:
> On Sun, Mar 01, 2020 at 07:21:03PM +0100, Jann Horn wrote:
>> On Sun, Mar 1, 2020 at 12:27 PM Bernd Edlinger
>> <bernd.edlinger@hotmail.de> wrote:
>>> The proposed solution is to have a second mutex that is
>>> used in mm_access, so it is allowed to continue while the
>>> dying threads are not yet terminated.
>>
>> Just for context: When I proposed something similar back in 2016,
>> https://lore.kernel.org/linux-fsdevel/20161102181806.GB1112@redhat.com/
>> was the resulting discussion thread. At least back then, I looked
>> through the various existing users of cred_guard_mutex, and the only
>> places that couldn't be converted to the new second mutex were
>> PTRACE_ATTACH and SECCOMP_FILTER_FLAG_TSYNC.
>>
>>
>> The ideal solution would IMO be something like this: Decide what the
>> new task's credentials should be *before* reaching de_thread(),
>> install them into a second cred* on the task (together with the new
>> dumpability), drop the cred_guard_mutex, and let ptrace_may_access()
>> check against both. After that, some further restructuring might even
>
> Hm, so essentially a private ptrace_access_cred member in task_struct?
> That would presumably also involve altering various LSM hooks to look at
> ptrace_access_cred.
>
> (Minor side-note, de_thread() takes a struct task_struct argument but
> only ever is passed current.)
>
>> allow the cred_guard_mutex to not be held across all of the VFS
>> operations that happen early on in execve, which may block
>> indefinitely. But that would be pretty complicated, so I think your
>> proposed solution makes sense for now, given that nobody has managed
>> to implement anything better in the last few years.
>
> Reading through the old threads and how often this issue came up, I tend
> to agree.
>
Okay, fine.
I managed to change Oleg's test case, into one that shows what exactly
is changed with this patch:
$ cat t.c
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/signal.h>
#include <sys/ptrace.h>
void *thread(void *arg)
{
ptrace(PTRACE_TRACEME, 0,0,0);
return NULL;
}
int main(void)
{
int f, pid = fork();
char mm[64];
if (!pid) {
pthread_t pt;
pthread_create(&pt, NULL, thread, NULL);
pthread_join(pt, NULL);
execlp("echo", "echo", "passed", NULL);
}
sleep(1);
sprintf(mm, "/proc/%d/mem", pid);
printf("open(%s)\n", mm);
f = open(mm, O_RDONLY);
printf("f = %d\n", f);
// this is not fixed! ptrace(PTRACE_ATTACH, pid, 0,0);
kill(pid, SIGCONT);
if (f >= 0)
close(f);
return 0;
}
$ gcc -pthread -Wall t.c
$ ./a.out
open(/proc/2802/mem)
f = 3
$ passed
previously this did block, how can I make a test case for this?
I am not so experienced in this matter.
Thanks
Bernd.
next prev parent reply other threads:[~2020-03-01 19:00 UTC|newest]
Thread overview: 203+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-01 11:27 [PATCH] exec: Fix a deadlock in ptrace Bernd Edlinger
2020-03-01 15:13 ` Aleksa Sarai
2020-03-01 15:58 ` Christian Brauner
2020-03-01 17:46 ` Bernd Edlinger
2020-03-01 18:20 ` Christian Brauner
2020-03-01 17:24 ` Bernd Edlinger
2020-03-01 18:21 ` Jann Horn
2020-03-01 18:52 ` Christian Brauner
2020-03-01 19:00 ` Bernd Edlinger [this message]
2020-03-01 20:00 ` Jann Horn
2020-03-01 20:34 ` [PATCHv2] " Bernd Edlinger
2020-03-02 6:38 ` Eric W. Biederman
2020-03-02 15:43 ` Bernd Edlinger
2020-03-02 15:57 ` Eric W. Biederman
2020-03-02 16:02 ` Bernd Edlinger
2020-03-02 16:17 ` Eric W. Biederman
2020-03-02 16:43 ` Jann Horn
2020-03-02 17:01 ` Bernd Edlinger
2020-03-02 17:37 ` Jann Horn
2020-03-02 17:42 ` christian
2020-03-02 18:08 ` Jann Horn
2020-03-02 20:10 ` [PATCHv3] " Bernd Edlinger
2020-03-02 20:28 ` Bernd Edlinger
2020-03-02 17:13 ` [PATCHv2] " Bernd Edlinger
2020-03-02 21:49 ` Eric W. Biederman
2020-03-02 22:00 ` Bernd Edlinger
2020-03-02 22:18 ` [PATCHv4] " Bernd Edlinger
2020-03-03 2:26 ` Kees Cook
2020-03-03 4:54 ` Bernd Edlinger
2020-03-03 5:29 ` Kees Cook
2020-03-03 8:08 ` Bernd Edlinger
2020-03-03 8:34 ` Christian Brauner
2020-03-03 8:43 ` Christian Brauner
2020-03-04 15:30 ` Christian Brauner
2020-03-03 8:58 ` Christian Brauner
2020-03-03 10:34 ` Bernd Edlinger
2020-03-03 11:23 ` Bernd Edlinger
2020-03-03 14:20 ` Christian Brauner
2020-03-03 13:02 ` [PATCHv5] " Bernd Edlinger
2020-03-03 15:18 ` Eric W. Biederman
2020-03-03 16:48 ` Bernd Edlinger
2020-03-03 17:01 ` Christian Brauner
2020-03-03 17:20 ` Christian Brauner
2020-03-03 20:08 ` Eric W. Biederman
2020-03-04 14:37 ` Bernd Edlinger
2020-03-04 16:33 ` Eric W. Biederman
2020-03-04 21:49 ` Bernd Edlinger
2020-03-04 21:56 ` [PATCHv6] " Bernd Edlinger
2020-03-05 18:36 ` Bernd Edlinger
2020-03-05 21:14 ` [PATCH 0/2] Infrastructure to allow fixing exec deadlocks Eric W. Biederman
2020-03-05 21:15 ` [PATCH 1/2] exec: Properly mark the point of no return Eric W. Biederman
2020-03-05 22:34 ` Bernd Edlinger
2020-03-06 5:19 ` Eric W. Biederman
2020-03-05 22:56 ` Bernd Edlinger
2020-03-06 5:09 ` Eric W. Biederman
2020-03-06 16:26 ` Bernd Edlinger
2020-03-06 17:16 ` Eric W. Biederman
2020-03-05 21:16 ` [PATCH 2/2] exec: Add a exec_update_mutex to replace cred_guard_mutex Eric W. Biederman
2020-03-05 21:51 ` Bernd Edlinger
2020-03-06 5:17 ` Eric W. Biederman
2020-03-06 11:46 ` Bernd Edlinger
2020-03-06 21:18 ` Eric W. Biederman
2020-03-06 19:16 ` Bernd Edlinger
2020-03-06 21:58 ` Eric W. Biederman
2020-03-06 22:29 ` Eric W. Biederman
2020-03-07 1:03 ` Eric W. Biederman
2020-03-08 12:58 ` [PATCH] exec: make de_thread alloc new signal struct earlier Bernd Edlinger
2020-03-08 18:12 ` Eric W. Biederman
2020-03-05 22:31 ` [PATCH 0/2] Infrastructure to allow fixing exec deadlocks Bernd Edlinger
2020-03-06 5:06 ` Eric W. Biederman
2020-03-08 21:34 ` [PATCH 0/5] " Eric W. Biederman
2020-03-08 21:35 ` [PATCH v2 1/5] exec: Only compute current once in flush_old_exec Eric W. Biederman
2020-03-09 13:56 ` Bernd Edlinger
2020-03-09 17:34 ` Eric W. Biederman
2020-03-09 17:56 ` Bernd Edlinger
2020-03-09 19:27 ` Bernd Edlinger
2020-03-10 20:17 ` Kees Cook
2020-03-10 21:12 ` Christian Brauner
2020-03-08 21:36 ` [PATCH v2 2/5] exec: Factor unshare_sighand out of de_thread and call it separately Eric W. Biederman
2020-03-09 19:28 ` Bernd Edlinger
2020-03-10 20:29 ` Kees Cook
2020-03-10 20:34 ` Bernd Edlinger
2020-03-10 20:57 ` Kees Cook
2020-03-10 21:21 ` Christian Brauner
2020-03-08 21:36 ` [PATCH v2 3/5] exec: Move cleanup of posix timers on exec out of de_thread Eric W. Biederman
2020-03-09 19:30 ` Bernd Edlinger
2020-03-09 19:59 ` Christian Brauner
2020-03-09 20:06 ` Eric W. Biederman
2020-03-09 20:17 ` Christian Brauner
2020-03-09 20:48 ` Eric W. Biederman
2020-03-10 8:55 ` Christian Brauner
2020-03-10 18:52 ` [PATCH] pidfd: Stop taking cred_guard_mutex Eric W. Biederman
2020-03-10 19:15 ` Christian Brauner
2020-03-10 19:16 ` Jann Horn
2020-03-10 19:27 ` Eric W. Biederman
2020-03-10 20:00 ` Jann Horn
2020-03-10 20:10 ` Jann Horn
2020-03-10 20:22 ` Bernd Edlinger
2020-03-11 6:11 ` Bernd Edlinger
2020-03-11 14:56 ` Jann Horn
2020-03-10 20:57 ` Eric W. Biederman
2020-03-10 21:29 ` Christian Brauner
2020-03-11 18:49 ` Kees Cook
2020-03-14 9:12 ` [PATCH] pidfd: Use new infrastructure to fix deadlocks in execve Bernd Edlinger
2020-03-10 20:16 ` [PATCH v2 3/5] exec: Move cleanup of posix timers on exec out of de_thread Kees Cook
2020-03-10 20:31 ` Kees Cook
2020-03-10 20:57 ` Jann Horn
2020-03-10 21:05 ` Eric W. Biederman
2020-03-10 21:22 ` Christian Brauner
2020-03-08 21:38 ` [PATCH v2 4/5] exec: Move exec_mmap right after de_thread in flush_old_exec Eric W. Biederman
2020-03-09 19:34 ` Bernd Edlinger
2020-03-09 19:45 ` Eric W. Biederman
2020-03-09 19:52 ` Bernd Edlinger
2020-03-09 19:58 ` Eric W. Biederman
2020-03-09 20:03 ` Bernd Edlinger
2020-03-09 20:35 ` Eric W. Biederman
2020-03-10 20:44 ` Kees Cook
2020-03-10 21:20 ` Eric W. Biederman
2020-03-10 20:47 ` Kees Cook
2020-03-10 21:09 ` Eric W. Biederman
2020-03-08 21:38 ` [PATCH v2 5/5] exec: Add a exec_update_mutex to replace cred_guard_mutex Eric W. Biederman
2020-03-09 13:45 ` Bernd Edlinger
2020-03-09 17:40 ` Eric W. Biederman
2020-03-09 18:01 ` Bernd Edlinger
2020-03-09 18:10 ` Eric W. Biederman
2020-03-09 18:24 ` Eric W. Biederman
2020-03-09 18:36 ` Eric W. Biederman
2020-03-09 18:47 ` Bernd Edlinger
2020-03-09 19:02 ` Eric W. Biederman
2020-03-09 19:24 ` Bernd Edlinger
2020-03-09 19:35 ` Eric W. Biederman
2020-03-09 19:39 ` Eric W. Biederman
2020-03-10 13:43 ` [PATCH 0/4] Use new infrastructure to fix deadlocks in execve Bernd Edlinger
2020-03-10 15:35 ` Eric W. Biederman
2020-03-10 17:44 ` [PATCH 0/4] Use new infrastructure in more simple cases Bernd Edlinger
2020-03-10 17:45 ` [PATCH 1/4] kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve Bernd Edlinger
2020-03-10 19:01 ` Eric W. Biederman
2020-03-10 19:42 ` Bernd Edlinger
2020-03-10 17:45 ` [PATCH 2/4] proc: " Bernd Edlinger
2020-03-11 18:59 ` Kees Cook
2020-03-11 19:10 ` Kees Cook
2020-03-11 19:38 ` Bernd Edlinger
2020-03-10 17:45 ` [PATCH 3/4] proc: io_accounting: " Bernd Edlinger
2020-03-10 19:06 ` Eric W. Biederman
2020-03-10 20:19 ` Bernd Edlinger
2020-03-10 21:25 ` Eric W. Biederman
2020-03-11 19:08 ` Kees Cook
2020-03-11 19:48 ` Bernd Edlinger
2020-03-11 19:48 ` Eric W. Biederman
2020-03-10 17:45 ` [PATCH 4/4] perf: " Bernd Edlinger
2020-03-10 13:43 ` [PATCH 1/4] exec: Fix a deadlock in ptrace Bernd Edlinger
2020-03-10 15:13 ` Eric W. Biederman
2020-03-10 15:17 ` Bernd Edlinger
2020-03-10 21:00 ` Kees Cook
2020-03-10 13:44 ` [PATCH 2/4] selftests/ptrace: add test cases for dead-locks Bernd Edlinger
2020-03-10 21:36 ` Kees Cook
2020-03-10 22:41 ` Dmitry V. Levin
2020-03-10 13:44 ` [PATCH 3/4] mm: docs: Fix a comment in process_vm_rw_core Bernd Edlinger
2020-03-11 18:53 ` Kees Cook
2020-03-10 13:44 ` [PATCH 4/4] kernel: doc: remove outdated comment cred.c Bernd Edlinger
2020-03-11 18:54 ` Kees Cook
2020-03-09 19:33 ` [PATCH v2 5/5] exec: Add a exec_update_mutex to replace cred_guard_mutex Dmitry V. Levin
2020-03-09 19:42 ` Eric W. Biederman
2020-03-10 20:55 ` Kees Cook
2020-03-10 21:02 ` Eric W. Biederman
2020-03-10 21:21 ` Jann Horn
2020-03-10 21:30 ` Eric W. Biederman
2020-03-10 23:21 ` Jann Horn
2020-03-11 0:15 ` Eric W. Biederman
2020-03-11 6:33 ` Bernd Edlinger
2020-03-11 16:29 ` Eric W. Biederman
2020-03-11 13:18 ` Qian Cai
2020-03-12 10:27 ` Kirill Tkhai
2020-03-12 12:24 ` Eric W. Biederman
2020-03-12 13:45 ` Kirill Tkhai
2020-03-12 14:38 ` Eric W. Biederman
2020-03-12 15:23 ` Kirill Tkhai
2020-03-13 1:05 ` Bernd Edlinger
2020-03-13 9:13 ` Kirill Tkhai
2020-03-14 9:11 ` [PATCH v3 " Bernd Edlinger
2020-03-17 8:56 ` Kirill Tkhai
2020-03-17 21:53 ` Bernd Edlinger
2020-03-18 12:22 ` Kirill Tkhai
2020-03-18 20:06 ` Bernd Edlinger
2020-03-19 7:13 ` Kirill Tkhai
2020-03-19 7:19 ` Bernd Edlinger
2020-03-19 9:11 ` [PATCH v4 3/5] " Bernd Edlinger
2020-03-19 9:13 ` Bernd Edlinger
2020-03-19 9:19 ` Greg Kroah-Hartman
2020-03-19 9:20 ` Bernd Edlinger
2020-03-21 22:53 ` Bernd Edlinger
2020-03-14 9:12 ` [PATCH 0/2] exec: Fix dead-lock in de_thread with ptrace_attach Bernd Edlinger
2020-03-14 9:12 ` [PATCH 1/2] " Bernd Edlinger
2020-03-14 9:13 ` [PATCH 2/2] doc: Update documentation of ->exec_*_mutex Bernd Edlinger
2020-03-14 9:57 ` [PATCH v2 5/5] exec: Add a exec_update_mutex to replace cred_guard_mutex Bernd Edlinger
2020-03-14 10:02 ` Bernd Edlinger
2020-03-17 8:58 ` Kirill Tkhai
2020-03-09 13:58 ` [PATCH 0/5] Infrastructure to allow fixing exec deadlocks Bernd Edlinger
2020-03-03 16:50 ` [PATCHv5] exec: Fix a deadlock in ptrace Christian Brauner
2020-03-02 12:28 ` [PATCHv2] " Oleg Nesterov
2020-03-02 15:56 ` Bernd Edlinger
2020-03-02 7:47 ` [PATCH] " Christian Brauner
2020-03-02 7:48 ` Christian Brauner
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=AM6PR03MB51702321B8A0E6A8C41ED3D5E4E60@AM6PR03MB5170.eurprd03.prod.outlook.com \
--to=bernd.edlinger@hotmail.de \
--cc=aarcange@redhat.com \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=anshuman.khandual@arm.com \
--cc=avagin@gmail.com \
--cc=bigeasy@linutronix.de \
--cc=christian.brauner@ubuntu.com \
--cc=christian@kellner.me \
--cc=corbet@lwn.net \
--cc=cyphar@cyphar.com \
--cc=david@redhat.com \
--cc=dhowells@redhat.com \
--cc=duyuyang@gmail.com \
--cc=ebiederm@xmission.com \
--cc=frederic@kernel.org \
--cc=gregkh@linuxfoundation.org \
--cc=jamorris@linux.microsoft.com \
--cc=jannh@google.com \
--cc=jgg@ziepe.ca \
--cc=keescook@chromium.org \
--cc=ldv@altlinux.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=shakeelb@google.com \
--cc=tglx@linutronix.de \
--cc=viro@zeniv.linux.org.uk \
/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).