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Date: Tue, 25 Oct 2022 14:47:15 +0200
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Pavel Machek <pavel@denx.de>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	Juergen Gross <jgross@suse.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>, xen-devel@lists.xenproject.org,
	Kees Cook <keescook@chromium.org>, Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 4.19 174/229] x86/entry: Work around Clang __bdos() bug
Message-ID: <Y1fa082Vhar2x1DM@kroah.com>
References: <20221024112959.085534368@linuxfoundation.org>
 <20221024113004.718917343@linuxfoundation.org>
 <20221024174127.GC25198@duo.ucw.cz>
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In-Reply-To: <20221024174127.GC25198@duo.ucw.cz>

On Mon, Oct 24, 2022 at 07:41:27PM +0200, Pavel Machek wrote:
> Hi!
> 
> > From: Kees Cook <keescook@chromium.org>
> > 
> > [ Upstream commit 3e1730842f142add55dc658929221521a9ea62b6 ]
> > 
> > Clang produces a false positive when building with CONFIG_FORTIFY_SOURCE=y
> > and CONFIG_UBSAN_BOUNDS=y when operating on an array with a dynamic
> > offset. Work around this by using a direct assignment of an empty
> > instance. Avoids this warning:
> > 
> > ../include/linux/fortify-string.h:309:4: warning: call to __write_overflow_field declared with 'warn
> > ing' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wat
> > tribute-warning]
> >                         __write_overflow_field(p_size_field, size);
> >                         ^
> > 
> > which was isolated to the memset() call in xen_load_idt().
> > 
> > Note that this looks very much like another bug that was worked around:
> > https://github.com/ClangBuiltLinux/linux/issues/1592
> 
> We don't have CONFIG_UBSAN_BOUNDS in 4.19, so maybe we don't need this
> one?

Good point, I'll drop this from 5.4.y and older now, thanks.

greg k-h