linux-hardening - Re: [PATCH] bcache: Silence memcpy() run-time false positive warnings

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Date:   Fri, 6 Jan 2023 11:01:05 +0100
From:   Thorsten Leemhuis <linux@...mhuis.info>
To:     Kees Cook <keescook@...omium.org>, Coly Li <colyli@...e.de>
Cc:     Kent Overstreet <kent.overstreet@...il.com>,
        linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] bcache: Silence memcpy() run-time false positive warnings

On 06.01.23 07:02, Kees Cook wrote:
> struct bkey has internal padding in a union, but it isn't always named
> the same (e.g. key ## _pad, key_p, etc). This makes it extremely hard
> for the compiler to reason about the available size of copies done
> against such keys. Use unsafe_memcpy() for now, to silence the many
> run-time false positive warnings:
> 
>   memcpy: detected field-spanning write (size 264) of single field "&i->j" at drivers/md/bcache/journal.c:152 (size 240)
>   memcpy: detected field-spanning write (size 24) of single field "&b->key" at drivers/md/bcache/btree.c:939 (size 16)
>   emcpy: detected field-spanning write (size 24) of single field "&temp.key" at drivers/md/bcache/extents.c:428 (size 16)

Thx for looking into this.

> Reported-by: Thorsten Leemhuis <linux@...mhuis.info>
> Link: https://lore.kernel.org/all/19200730-a3ba-6f4f-bb81-71339bdbbf73@leemhuis.info/

Credit where credit is due, this should be:

Reported-by: Alexandre Pereira <alexpereira@...root.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216785

> Cc: Coly Li <colyli@...e.de>
> […]

Ciao, Thorsten