Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Sat, 26 May 2018 10:53:04 -0700
From: Casey Schaufler <>
To: Salvatore Mesoraca <>,
 Alexey Dobriyan <>
Cc: Kernel Hardening <>,,,, Andrew Morton <>,
 Akinobu Mita <>, Dmitry Vyukov <>,
 Arnd Bergmann <>, Davidlohr Bueso <>,
 Kees Cook <>
Subject: Re: [PATCH] proc: prevent a task from writing on its own /proc/*/mem

On 5/26/2018 10:30 AM, Salvatore Mesoraca wrote:
> 2018-05-26 17:48 GMT+02:00 Alexey Dobriyan <>:
>> On Sat, May 26, 2018 at 04:50:46PM +0200, Salvatore Mesoraca wrote:
>>> Prevent a task from opening, in "write" mode, any /proc/*/mem
>>> file that operates on the task's mm.
>>> /proc/*/mem is mainly a debugging means and, as such, it shouldn't
>>> be used by the inspected process itself.
>>> Current implementation always allow a task to access its own
>>> /proc/*/mem file.
>>> A process can use it to overwrite read-only memory, making
>>> pointless the use of security_file_mprotect() or other ways to
>>> enforce RO memory.
>> You can do it in security_ptrace_access_check()
> No, because that hook is skipped when mm == current->mm:
>> or security_file_open()
> This is true, but it looks a bit overkill to me, especially since many of
> the macros/functions used to handle proc's files won't be in scope
> for an external LSM.
> Is there any particular reason why you prefer it done via LSM?

If you did a Yama style LSM it would be easy to configure.
Even though it might make no sense to allow this behavior,
someone, somewhere is counting on it.

> Thank you,
> Salvatore
> --
> To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
> the body of a message to
> More majordomo info at

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.