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Message-ID: <60fd581a57945efc1c6a2a8d58a88301a79e51ec.camel@mediatek.com>
Subject: Re: [PATCH] mt76: fix monitor mode crash with sdio driver
From:   Deren Wu <deren.wu@mediatek.com>
To:     Felix Fietkau <nbd@nbd.name>,
        Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
CC:     Sean Wang <sean.wang@mediatek.com>,
        Soul Huang <Soul.Huang@mediatek.com>,
        YN Chen <YN.Chen@mediatek.com>,
        Leon Yen <Leon.Yen@mediatek.com>,
        "Eric-SY Chang" <Eric-SY.Chang@mediatek.com>,
        KM Lin <km.lin@mediatek.com>,
        Robin Chiu <robin.chiu@mediatek.com>,
        CH Yeh <ch.yeh@mediatek.com>, Posh Sun <posh.sun@mediatek.com>,
        Eric Liang <Eric.Liang@mediatek.com>,
        Stella Chang <Stella.Chang@mediatek.com>,
        Evelyn Tsai <evelyn.tsai@mediatek.com>,
        "Ryder Lee" <ryder.lee@mediatek.com>,
        Shayne Chen <shayne.chen@mediatek.com>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        linux-mediatek <linux-mediatek@lists.infradead.org>
Date:   Thu, 3 Mar 2022 17:12:58 +0800
In-Reply-To: <d065e4492a9e995d6ebe95c7ad8a1ec6183f56ef.1646277169.git.deren.wu@mediatek.com>
References: <d065e4492a9e995d6ebe95c7ad8a1ec6183f56ef.1646277169.git.deren.wu@mediatek.com>
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Hi Felix,

I need to submit v2 patch. Please drop this one.


Thanks,
Deren


On Thu, 2022-03-03 at 11:28 +0800, Deren Wu wrote:
> From: Deren Wu <deren.wu@mediatek.com>
> 
> mt7921s driver may receive frames with fragment buffers. If there is
> a
> CTS packet received in monitor mode, the payload is 10 bytes only and
> need 6 bytes header padding after RXD buffer. However, only RXD in
> the
> first linear buffer, if we pull buffer size RXD-size+6 bytes with
> skb_pull(), that would trigger "BUG_ON(skb->len < skb->data_len)" in
> __skb_pull().
> 
> To avoid the nonlinear buffer issue, enlarge the RXD size from 128 to
> 136 to make sure all MCU operation in linear buffer.
> 
> 136 = 128 + 8
>   128 : RXD size
>   8   : max header padding length
> 
> [   52.007562] kernel BUG at include/linux/skbuff.h:2313!
> [   52.007578] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> [   52.007987] pc : skb_pull+0x48/0x4c
> [   52.008015] lr : mt7921_queue_rx_skb+0x494/0x890 [mt7921_common]
> [   52.008361] Call trace:
> [   52.008377]  skb_pull+0x48/0x4c
> [   52.008400]  mt76s_net_worker+0x134/0x1b0 [mt76_sdio
> 35339a92c6eb7d4bbcc806a1d22f56365565135c]
> [   52.008431]  __mt76_worker_fn+0xe8/0x170 [mt76
> ef716597d11a77150bc07e3fdd68eeb0f9b56917]
> [   52.008449]  kthread+0x148/0x3ac
> [   52.008466]  ret_from_fork+0x10/0x30
> 
> Co-developed-by: Sean Wang <sean.wang@mediatek.com>
> Signed-off-by: Sean Wang <sean.wang@mediatek.com>
> Signed-off-by: Deren Wu <deren.wu@mediatek.com>
> ---
>  drivers/net/wireless/mediatek/mt76/mt76.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h
> b/drivers/net/wireless/mediatek/mt76/mt76.h
> index 5e10fe156926..4f4ce3b3df54 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt76.h
> @@ -19,7 +19,8 @@
>  
>  #define MT_MCU_RING_SIZE	32
>  #define MT_RX_BUF_SIZE		2048
> -#define MT_SKB_HEAD_LEN		128
> +/* 136 = 128+8. 128: RXD, 8:max header padding*/
> +#define MT_SKB_HEAD_LEN		136
>  
>  #define MT_MAX_NON_AQL_PKT	16
>  #define MT_TXQ_FREE_THR		32