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

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Message-ID: <202408092104.FCE51021@keescook>
Date: Fri, 9 Aug 2024 21:06:20 -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 Sat, Aug 10, 2024 at 12:52:16AM +0000, Brian Mak wrote:
> On Aug 6, 2024, at 10:21 PM, Kees Cook <kees@...nel.org> wrote:
> > 
> > On Tue, 06 Aug 2024 18:16:02 +0000, Brian Mak wrote:
> >> 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.
> >> 
> >> [...]
> > 
> > While waiting on rr test validation, and since we're at the start of the
> > dev cycle, I figure let's get this into -next ASAP to see if anything
> > else pops out. We can drop/revise if there are problems. (And as always,
> > I will add any Acks/Reviews/etc that show up on the thread.)
> > 
> > Applied to for-next/execve, thanks!
> > 
> > [1/1] binfmt_elf: Dump smaller VMAs first in ELF cores
> >      https://urldefense.com/v3/__https://git.kernel.org/kees/c/9c531dfdc1bc__;!!NEt6yMaO-gk!FK3UfXVndoYpve8Y7q7vacIoHOrTj2nJgSJbugqUB5LfciKy0_Xvit9aXz_XCWlXHpdRQO2ArP0$
> 
> Thanks, Kees! And, thanks Linus + Eric for taking the time to comment on
> this.
> 
> Regarding the rr tests, it was not an easy task to get the environment
> set up to do this, but I did it and was able to run the tests. The rr
> tests require a lot of kernel config options and there's no list
> documenting what's needed anywhere...

Thanks for suffering through that!

> All the tests pass except for the sioc and sioc-no-syscallbuf tests.
> However, these test failures are due to an incompatibility with the
> network adapter I'm using. It seems that it only likes older network
> adapters. I've switched my virtualized network adapter twice now, and
> each time, the test gets a bit further than the previous time. Will
> continue trying different network adapters until something hopefully
> works. In any case, since this error isn't directly related to my
> changes and the rest of the tests pass, then I think we can be pretty
> confident that this change is not breaking rr.

Perfect! Okay, we'll keep our eyes open for any reports of breakage. :)

-Kees

-- 
Kees Cook