linux-hardening - Re: [PATCH] Bluetooth: hci_conn: Refactor hci_bind

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Date:   Sat, 28 Jan 2023 14:44:54 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Luiz Augusto von Dentz <luiz.von.dentz@...el.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] Bluetooth: hci_conn: Refactor hci_bind_bis() since it
 always succeeds

On Fri, Jan 27, 2023 at 04:51:54PM -0800, Kees Cook wrote:
> The compiler thinks "conn" might be NULL after a call to hci_bind_bis(),
> which cannot happen. Avoid any confusion by just making it not return a
> value since it cannot fail. Fixes the warnings seen with GCC 13:
> 
> In function 'arch_atomic_dec_and_test',
>     inlined from 'atomic_dec_and_test' at ../include/linux/atomic/atomic-instrumented.h:576:9,
>     inlined from 'hci_conn_drop' at ../include/net/bluetooth/hci_core.h:1391:6,
>     inlined from 'hci_connect_bis' at ../net/bluetooth/hci_conn.c:2124:3:
> ../arch/x86/include/asm/rmwcc.h:37:9: warning: array subscript 0 is outside array bounds of 'atomic_t[0]' [-Warray-bounds=]
>    37 |         asm volatile (fullop CC_SET(cc) \
>       |         ^~~
> ...
> In function 'hci_connect_bis':
> cc1: note: source object is likely at address zero
> 
> Fixes: eca0ae4aea66 ("Bluetooth: Add initial implementation of BIS connections")
...
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  net/bluetooth/hci_conn.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)

Is this really a 'fix' ?

In any case, the change looks good to me.

Reviewed-by: Simon Horman <simon.horman@...igine.com>