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From: Jonny Grant <jg@jguk.org>
To: mtk.manpages@gmail.com, Jakub Wilk <jwilk@jwilk.net>
Cc: linux-man <linux-man@vger.kernel.org>
Subject: Re: core(5)
Date: Sat, 6 Jun 2020 22:16:28 +0100
Message-ID: <a504a2ab-32d2-ad39-295f-47a1d5de2f34@jguk.org> (raw)
In-Reply-To: <CAKgNAkiqfE4WETiE4VBMGpnDM0twtB0B6pbMyuoMT5+WWrpKvw@mail.gmail.com>



On 06/06/2020 20:39, Michael Kerrisk (man-pages) wrote:
> On Sat, 6 Jun 2020 at 20:32, Jakub Wilk <jwilk@jwilk.net> wrote:
>>
>> * Jonny Grant <jg@jguk.org>, 2020-06-06, 16:45:
>>>>> 3) Could i ask to clarify my understanding. For this "The binary
>>>>> being executed by the process does not have read permission enabled."
>>>>> -- is this when the binary permissions are changed after it starts
>>>>> running?
>>>> No, AFAICS the permission check is done when the process starts.
>>> How can the process start if the binary file doesn't have read
>>> permissions enabled?
>>
>> It's a bit weird, but the kernel doesn't mind:
>>
>>     $ cp /bin/ls .
>>     $ chmod a-r ls
>>     $ ./ls -l ls
>>     --wx--x--x 1 jwilk jwilk 138856 Jun  6 20:22 ls
> 
> And from core(5):
> 
>         There are various circumstances in which a core dump file  is  not
>         produced:
>         ...
>         *  The binary being executed by the process  does  not  have  read
>            permission enabled.
> 
> So, the binary can be executed, but not read, and will not do a core
> dump (since that might be readable).
> 
> Thanks,
> 
> Michael

Hi Michael, Jakub,

It sounds like a good security feature. Could that be documented on the man page as the reason?

ie something like this:

*  The binary being executed by the process  does  not  have  read
permission enabled, therefore a core file would reveal information in a readable file, so it cannot be dumped.

Cheers
Jonny

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-06 13:18 core(5) Jonny Grant
2020-06-06 14:50 ` core(5) Jakub Wilk
2020-06-06 15:45   ` core(5) Jonny Grant
2020-06-06 18:32     ` core(5) Jakub Wilk
2020-06-06 19:39       ` core(5) Michael Kerrisk (man-pages)
2020-06-06 21:16         ` Jonny Grant [this message]
2020-06-08 16:18           ` core(5) Michael Kerrisk (man-pages)
2020-06-08 16:06 ` core(5) Michael Kerrisk (man-pages)

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