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

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Message-Id: <21D2A2BB-F442-480D-8B66-229E8C4A63D3@toblux.com>
Date: Wed, 2 Oct 2024 11:18:57 +0200
From: Thorsten Blum <thorsten.blum@...lux.com>
To: Kees Cook <kees@...nel.org>
Cc: Jan Hendrik Farr <kernel@...rr.cc>,
 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 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)?

Otherwise adding __counted_by() might be a slippery slope for a long
time and the edge cases don't seem to be that rare anymore.

Thanks,
Thorsten

[1] https://lore.kernel.org/all/20240909162725.1805-2-thorsten.blum@toblux.com/
[2] https://lore.kernel.org/all/20240923213809.235128-2-thorsten.blum@linux.dev/