linux-kernel - Re: process '/usr/bin/rsync' started with executable stack

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Date:   Wed, 24 Jun 2020 00:12:18 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Christian Kujau <lists@...dbynature.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Willy Tarreau <w@....eu>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Kees Kook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Subject: Re: process '/usr/bin/rsync' started with executable stack

On Tue, Jun 23, 2020 at 10:39:26AM -0700, Christian Kujau wrote:
> Hi,
> 
> exactly this[0] happened today, on a 5.6.5 kernel:
> 
>   process '/usr/bin/rsync' started with executable stack
> 
> But I can't reproduce this message, and rsync (v3.2.0, not exactly 
> abandonware) runs several times a day, so to repeat Andrew's questions[0] 
> from last year:
> 
>   > What are poor users supposed to do if this message comes out? 
>   > Hopefully google the message and end up at this thread.  What do you
>   > want to tell them?
> 
> Also, the PID is missing from that message.

That's intentional. I for one hate pids.

> I had some long running rsync 
> processes running earlier, maybe the RWE status would have been visible in 
> /proc/$PID/map, or somewhere else maybe?

If you think process is still running, /proc/*/maps should have 'rwxp'
indeed. You can do quick

	$ grep -e '\[stack\]' /proc/*/maps'

to find it.

> $ checksec --format=json --extended --file=`which rsync` | jq
> {
>   "/usr/bin/rsync": {
>     "relro": "full",
>     "canary": "yes",
>     "nx": "no",
>     "pie": "yes",
>     "clangcfi": "no",
>     "safestack": "no",
>     "rpath": "no",
>     "runpath": "no",
>     "symbols": "no",
>     "fortify_source": "yes",
>     "fortified": "10",
>     "fortify-able": "19"
>   }
> }

	$ readelf -l /usr/bin/rsync | grep GNU_STACK -A1
	  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
	                 0x0000000000000000 0x0000000000000000  RW     0x10