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Date:   Mon, 09 Oct 2023 17:36:55 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Arnd Bergmann" <arnd@kernel.org>,
        "Marcel Holtmann" <marcel@holtmann.org>,
        "Johan Hedberg" <johan.hedberg@gmail.com>,
        "Luiz Augusto von Dentz" <luiz.dentz@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        "Eric Dumazet" <edumazet@google.com>,
        "Jakub Kicinski" <kuba@kernel.org>,
        "Paolo Abeni" <pabeni@redhat.com>, "Lee, Chun-Yi" <jlee@suse.com>
Cc:     "Kees Cook" <keescook@chromium.org>,
        "Luiz Augusto von Dentz" <luiz.von.dentz@intel.com>,
        stable@vger.kernel.org,
        "Iulia Tanasescu" <iulia.tanasescu@nxp.com>,
        "Wenjia Zhang" <wenjia@linux.ibm.com>,
        linux-bluetooth@vger.kernel.org, Netdev <netdev@vger.kernel.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Bluetooth: mark bacmp() and bacpy() as __always_inline
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On Mon, Oct 9, 2023, at 15:48, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@chromium.org>
> Cc: Lee, Chun-Yi <jlee@suse.com>
> Cc: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> Cc: Marcel Holtmann <marcel@holtmann.org>
> Cc: stable@vger.kernel.org
> Signed-off-by: Arnd Bergmann <arnd@arndb.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