linux-kernel - Re: [PATCH 2/2] Revert "pstore: Honor dmesg

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Date:   Fri, 18 Aug 2017 08:24:37 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Nick Kralevich <nnk@...gle.com>,
        Sebastian Schmidt <yath@...h.de>,
        Tony Luck <tony.luck@...el.com>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Patrick Tjin <pattjin@...gle.com>,
        Mark Salyzyn <salyzyn@...gle.com>
Subject: Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg
 dumps"

Hello,

On (08/17/17 16:01), Kees Cook wrote:
> On Wed, Aug 16, 2017 at 6:29 PM, Sergey Senozhatsky
> <sergey.senozhatsky.work@...il.com> wrote:
> > can we accidentally "leak" kernel pointers or some other critical
> > info? kptr_restrict requires CAP_SYSLOG and pstore read used to
> > require CAP_SYSLOG, but it seems that now we can bypass it by
> > letting "entirely unprivileged groups" to read pstore. is there
> > something to be concerned about (or at least mention it in the
> > commit messages)?
> 
> I can expand the commit message a bit more, sure.

that would be lovely. please do.

> There may be sensitive things in pstorefs, and it's up to a system builder
> to decide how they want to deal with that risk. Most users of pstore
> don't mount with update_ms=N so pstorefs contains (mostly) old
> addresses.

I see...

> Without this change, though, a builder can't give permissions to an
> unprivileged crash dump process without also giving it CAP_SYSLOG which
> has much MORE privilege that it would need (reading and wiping _current_
> dmesg, for example).

ok, the "CAP_SYSLOG and _current_ dmesg" point is surely interesting.
could you please also add this to the commit message?


FWIW, both patches

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

	-ss