linux-kernel - Re: [REGRESSION][BISECTED] erroneous buffer overflow detected in bch2_xattr

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Message-ID: <Zv8VDKWN1GzLRT-_@archlinux>
Date: Fri, 4 Oct 2024 00:05:00 +0200
From: Jan Hendrik Farr <kernel@...rr.cc>
To: Kees Cook <kees@...nel.org>
Cc: Thorsten Blum <thorsten.blum@...lux.com>, kent.overstreet@...ux.dev,
	regressions@...ts.linux.dev, linux-bcachefs@...r.kernel.org,
	linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
	ardb@...nel.org, morbo@...gle.com
Subject: Re: [REGRESSION][BISECTED] erroneous buffer overflow detected in
 bch2_xattr_validate

On 03 14:23:20, Kees Cook wrote:
> On Wed, Oct 02, 2024 at 11:18:57AM +0200, Thorsten Blum wrote:
> > On 28. Sep 2024, at 22:34, Kees Cook <kees@...nel.org> wrote:
> > > [...]
> > > 
> > > Sorry, I've been out of commission with covid. Globally disabling this
> > > macro for clang is not the right solution (way too big a hammer).
> > > 
> > > Until Bill has a fix, we can revert commit
> > > 86e92eeeb23741a072fe7532db663250ff2e726a, as the problem is limited to
> > > certain situations where 'counted_by' is in use.
> > 
> > I already encountered two other related __counted_by() issues [1][2]
> > that are now being reverted. Would it be an option to disable it
> > globally, but only for Clang < v19 (where it looks like it'll be fixed)?
> 
> Yeah, once we have a solid fix (so we have a known Clang version to
> target), I'll want counted_by disabled in versions prior to that.
> 

Just to clarify: There are two separate issues. One was __bdos returning
0 (or sometimes other garbage). That one is fixed in main by [1] (so
will presumably be fixed in 19.1.2). The second is __bdos sometimes being off
by 4 bytes. That could be addressed by open PR [2].

[1] https://github.com/llvm/llvm-project/pull/110497
[2] https://github.com/llvm/llvm-project/pull/111015