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

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Message-ID: <202410031424.45E5D19@keescook>
Date: Thu, 3 Oct 2024 14:28:01 -0700
From: Kees Cook <kees@...nel.org>
To: Jan Hendrik Farr <kernel@...rr.cc>
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 Thu, Oct 03, 2024 at 05:17:08PM +0200, Jan Hendrik Farr wrote:
> gcc currently says that the __bdos of struct containing a flexible array
> member is:
> 
> sizeof(<whole struct>) + sizeof(<flexible array element>) * <count>
> 
> clang however does the following:
> 
> max(sizeof(<whole struct>), offsetof(<flexible array member>) + sizeof(<flexible array element>) * <count>)

Clang's calculation seems very wrong. I would expect it to match GCC's.

-- 
Kees Cook