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Date: Sat, 26 May 2018 19:30:47 +0200
From: Salvatore Mesoraca <>
To: 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

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?

Thank you,


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