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References: <20210712134430.19372-1-yuehaibing@huawei.com>
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From:   Alexander Aring <alex.aring@gmail.com>
Date:   Tue, 13 Jul 2021 09:32:38 -0400
Message-ID: <CAB_54W62WZCcPintGnu-kqzCmgAH7EsJxP9oaeD2NVZ03e_2Wg@mail.gmail.com>
Subject: Re: [PATCH] nl802154: Fix type check in nl802154_new_interface()
To:     YueHaibing <yuehaibing@huawei.com>
Cc:     Stefan Schmidt <stefan@datenfreihafen.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Marcel Holtmann <marcel@holtmann.org>,
        linux-wpan - ML <linux-wpan@vger.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org>,
        kernel list <linux-kernel@vger.kernel.org>
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Hi,

On Mon, 12 Jul 2021 at 09:49, YueHaibing <yuehaibing@huawei.com> wrote:
>
> We got this UBSAN warning:
>
> UBSAN: shift-out-of-bounds in net/ieee802154/nl802154.c:920:44
> shift exponent -1 is negative
> CPU: 3 PID: 8258 Comm: repro Not tainted 5.13.0+ #222
> Call Trace:
>  dump_stack_lvl+0x8d/0xcf
>  ubsan_epilogue+0xa/0x4e
>  __ubsan_handle_shift_out_of_bounds+0x161/0x182
>  nl802154_new_interface+0x3bf/0x3d0
>  genl_family_rcv_msg_doit.isra.15+0x12d/0x170
>  genl_rcv_msg+0x11a/0x240
>  netlink_rcv_skb+0x69/0x160
>  genl_rcv+0x24/0x40
>
> NL802154_IFTYPE_UNSPEC is -1, so enum nl802154_iftype type now
> is a signed integer, which is assigned by nla_get_u32 in
> nl802154_new_interface(), this may cause type is negative and trigger
> this warning.

I think this is not the right fix, the fix is to change the UAPI that
NL802154_IFTYPE_UNSPEC fits into the netlink range of U32. I will
prepare a fix for that, it should still be backwards compatible.

- Alex