linux-kernel - Re: [PATCH] Bluetooth: mark bacmp() and bacpy() as __always

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Message-Id: <2abaad09-b6e0-4dd5-9796-939f20804865@app.fastmail.com>
Date:   Mon, 09 Oct 2023 17:36:55 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Arnd Bergmann" <arnd@...nel.org>,
        "Marcel Holtmann" <marcel@...tmann.org>,
        "Johan Hedberg" <johan.hedberg@...il.com>,
        "Luiz Augusto von Dentz" <luiz.dentz@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric Dumazet" <edumazet@...gle.com>,
        "Jakub Kicinski" <kuba@...nel.org>,
        "Paolo Abeni" <pabeni@...hat.com>, "Lee, Chun-Yi" <jlee@...e.com>
Cc:     "Kees Cook" <keescook@...omium.org>,
        "Luiz Augusto von Dentz" <luiz.von.dentz@...el.com>,
        stable@...r.kernel.org,
        "Iulia Tanasescu" <iulia.tanasescu@....com>,
        "Wenjia Zhang" <wenjia@...ux.ibm.com>,
        linux-bluetooth@...r.kernel.org, Netdev <netdev@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Bluetooth: mark bacmp() and bacpy() as __always_inline

On Mon, Oct 9, 2023, at 15:48, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
>
> These functions are simple wrappers around memcmp() and memcpy(), which
> contain compile-time checks for buffer overflow. Something in gcc-13 and
> likely other versions makes this trigger a warning when the functions
> are not inlined and the compiler misunderstands the buffer length:
>
> In file included from net/bluetooth/hci_event.c:32:
> In function 'bacmp',
>     inlined from 'hci_conn_request_evt' at 
> net/bluetooth/hci_event.c:3276:7:
> include/net/bluetooth/bluetooth.h:364:16: error: 'memcmp' specified 
> bound 6 exceeds source size 0 [-Werror=stringop-overread]
>   364 |         return memcmp(ba1, ba2, sizeof(bdaddr_t));
>       |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Use the __always_inline annotation to ensure that the helpers are
> correctly checked. This has no effect on the actual correctness
> of the code, but avoids the warning. Since the patch that introduced
> the warning is marked for stable backports, this one should also
> go that way to avoid introducing build regressions.
>
> Fixes: d70e44fef8621 ("Bluetooth: Reject connection with the device 
> which has same BD_ADDR")
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Lee, Chun-Yi <jlee@...e.com>
> Cc: Luiz Augusto von Dentz <luiz.von.dentz@...el.com>
> Cc: Marcel Holtmann <marcel@...tmann.org>
> Cc: stable@...r.kernel.org
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Sorry, I have to retract this, something went wrong on my
testing and I now see the same problem in some configs regardless
of whether the patch is applied or not.

     Arnd