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From: Andy Lutomirski <luto@kernel.org>
To: Andrei Vagin <avagin@gmail.com>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org
Cc: linux-um@lists.infradead.org, criu@openvz.org, avagin@google.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Dmitry Safonov <0x7f454c46@gmail.com>,
	Ingo Molnar <mingo@redhat.com>, Jeff Dike <jdike@addtoit.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Richard Weinberger <richard@nod.at>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 0/4 POC] Allow executing code and syscalls in another address space
Date: Fri, 2 Jul 2021 15:44:41 -0700	[thread overview]
Message-ID: <6073e4c6-6fe8-0448-4586-5d04d7154164@kernel.org> (raw)
In-Reply-To: <20210414055217.543246-1-avagin@gmail.com>

On 4/13/21 10:52 PM, Andrei Vagin wrote:

> process_vm_exec has two modes:
> 
> * Execute code in an address space of a target process and stop on any
>   signal or system call.

We already have a perfectly good context switch mechanism: context
switches.  If you execute code, you are basically guaranteed to be
subject to being hijacked, which means you pretty much can't allow
syscalls.  But there's a lot of non-syscall state, and I think context
switching needs to be done with extreme care.

(Just as example, suppose you switch mms, then set %gs to point to the
LDT, then switch back.  Now you're in a weird state.  With %ss the plot
is a bit thicker.  And there are emulated vsyscalls and such.)

If you, PeterZ, and the UMCG could all find an acceptable, efficient way
to wake-and-wait so you can switch into an injected task in the target
process and switch back quickly, then I think a much nicer solution will
become available.

> 
> * Execute a system call in an address space of a target process.

I could get behind this, but there are plenty of cans of worms to watch
out for.  Serious auditing would be needed.

  parent reply	other threads:[~2021-07-02 22:44 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-14  5:52 [PATCH 0/4 POC] Allow executing code and syscalls in another address space Andrei Vagin
2021-04-14  5:52 ` [PATCH 1/4] signal: add a helper to restore a process state from sigcontex Andrei Vagin
2021-04-14  5:52 ` [PATCH 2/4] arch/x86: implement the process_vm_exec syscall Andrei Vagin
2021-04-14 17:09   ` Oleg Nesterov
2021-04-23  6:59     ` Andrei Vagin
2021-06-28 16:13   ` Jann Horn
2021-06-28 16:30     ` Andy Lutomirski
2021-06-28 17:14       ` Jann Horn
2021-06-28 18:18         ` Eric W. Biederman
2021-06-29  1:01           ` Andrei Vagin
2021-07-02  6:22     ` Andrei Vagin
2021-07-02 11:51       ` Jann Horn
2021-07-02 20:40         ` Andy Lutomirski
2021-07-02  8:51   ` Peter Zijlstra
2021-07-02 22:21     ` Andrei Vagin
2021-07-02 20:56   ` Jann Horn
2021-07-02 22:48     ` Andrei Vagin
2021-04-14  5:52 ` [PATCH 3/4] arch/x86: allow to execute syscalls via process_vm_exec Andrei Vagin
2021-04-14  5:52 ` [PATCH 4/4] selftests: add tests for process_vm_exec Andrei Vagin
2021-04-14  6:46 ` [PATCH 0/4 POC] Allow executing code and syscalls in another address space Jann Horn
2021-04-14 22:10   ` Andrei Vagin
2021-07-02  6:57   ` Andrei Vagin
2021-07-02 15:12     ` Jann Horn
2021-07-18  0:38       ` Andrei Vagin
2021-04-14  7:22 ` Anton Ivanov
2021-04-14  7:34   ` Johannes Berg
2021-04-14  9:24     ` Benjamin Berg
2021-04-14 10:27 ` Florian Weimer
2021-04-14 11:24   ` Jann Horn
2021-04-14 12:20     ` Florian Weimer
2021-04-14 13:58       ` Jann Horn
2021-04-16 19:29 ` Kirill Smelkov
2021-04-17 16:28 ` sbaugh
2021-07-02 22:44 ` Andy Lutomirski [this message]
2021-07-18  1:34   ` Andrei Vagin

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