linux-kernel - Re: [PATCH 0/3] Dump command line of faulting process to syslog

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Date:   Thu, 4 Aug 2022 02:06:38 -0700
From:   Josh Triplett <josh@...htriplett.org>
To:     Helge Deller <deller@....de>
Cc:     linux-arch@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Dump command line of faulting process to syslog

On Thu, Aug 04, 2022 at 10:39:52AM +0200, Helge Deller wrote:
> On 8/4/22 10:09, Josh Triplett wrote:
> > On Tue, Aug 02, 2022 at 09:40:50PM +0200, Helge Deller wrote:
> >> On 8/1/22 18:57, Josh Triplett wrote:
> >>> However, it's also an information disclosure in various ways. The
> >>> arguments of a program are often more sensitive than the name, and logs
> >>> have a tendency to end up in various places, such as bug reports.
> >>>
> >>> An example of how this can be an issue:
> >>> - You receive an email or other message with a sensitive link to follow
> >>> - You open the link, which launches `firefox https://...`
> >>> - You continue browsing from that window
> >>> - Firefox crashes (and recovers and restarts, so you don't think
> >>>   anything of it)
> >>> - Later, you report a bug on a different piece of software, and the bug
> >>>   reporting process includes a copy of the kernel log
> >>
> >> Yes, that's a possible way how such information can leak.
> >>
> >>> I am *not* saying that we shouldn't do this; it seems quite helpful.
> >>> However, I think we need to arrange to treat this as sensitive
> >>> information, similar to kptr_restrict.
[...]
> > I don't think we should overload the meaning of dmesg_restrict. But
> > overloading kptr_restrict seems reasonable to me. (Including respecting
> > kptr_restrict==2 by not showing this at all.)
> 
> I'm fine with kptr_restrict, but I'm puzzled for which value of kptr_restrict
> the command line should be shown then.
> By looking at the meaning of kptr_restrict, I think the command line should be
> hidden for values 0-2.
> Do you suggest to add a new value "3" or am I missing something?

I'm suggesting treating it the same as a pointer value:

0: always show command line
1: show command line if read by privileged caller
2: never show command line

That could either use kptr_restrict or use a separate cmdline_restrict.