linux-kernel - Re: [PATCH v3] binfmt_elf: Dump smaller VMAs first in ELF cores

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Message-ID: <202408121123.FBAE8191A3@keescook>
Date: Mon, 12 Aug 2024 11:25:10 -0700
From: Kees Cook <kees@...nel.org>
To: Brian Mak <makb@...iper.net>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v3] binfmt_elf: Dump smaller VMAs first in ELF cores

On Mon, Aug 12, 2024 at 06:21:15PM +0000, Brian Mak wrote:
> On Aug 12, 2024, at 11:05 AM, Kees Cook <kees@...nel.org> wrote
> 
> > On Sat, Aug 10, 2024 at 07:28:44AM -0500, Eric W. Biederman wrote:
> >> Brian Mak <makb@...iper.net> writes:
> >> 
> >>> Large cores may be truncated in some scenarios, such as with daemons
> >>> with stop timeouts that are not large enough or lack of disk space. This
> >>> impacts debuggability with large core dumps since critical information
> >>> necessary to form a usable backtrace, such as stacks and shared library
> >>> information, are omitted.
> >>> 
> >>> We attempted to figure out which VMAs are needed to create a useful
> >>> backtrace, and it turned out to be a non-trivial problem. Instead, we
> >>> try simply sorting the VMAs by size, which has the intended effect.
> >>> 
> >>> By sorting VMAs by dump size and dumping in that order, we have a
> >>> simple, yet effective heuristic.
> >> 
> >> To make finding the history easier I would include:
> >> v1: https://urldefense.com/v3/__https://lkml.kernel.org/r/CB8195AE-518D-44C9-9841-B2694A5C4002@juniper.net__;!!NEt6yMaO-gk!DavIB4o54KGrCPK44iq9_nJrOpKMJxUAlazBVF6lfKwmMCgLD_NviY088SQXriD19pS0rwhadvc$
> >> v2: https://urldefense.com/v3/__https://lkml.kernel.org/r/C21B229F-D1E6-4E44-B506-A5ED4019A9DE@juniper.net__;!!NEt6yMaO-gk!DavIB4o54KGrCPK44iq9_nJrOpKMJxUAlazBVF6lfKwmMCgLD_NviY088SQXriD19pS0G7RQv4o$
> >> 
> >> Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> >> 
> >> As Kees has already picked this up this is quite possibly silly.
> >> But *shrug* that was when I was out.
> > 
> > I've updated the trailers. Thanks for the review!
> 
> Hi Kees,
> 
> Thanks! I think you added it to the wrong commit though.

Ugh. Time for more coffee. Thanks; fixed. I need to update my "b4" -- it
was hanging doing the trailers update so I did it myself manually...
That'll teach me. ;)

> tests. Since all the other tests pass, I'm just going to leave it at
> that.

Yeah, I think you're good. Thank you for taking the time to test rr!

-- 
Kees Cook