[PATCH] mt76: mt7921: fix the coredump is being truncated

[Lorenzo Bianconi]

> From: Sean Wang <sean.wang at mediatek.com>
> 
> Fix the maximum size of the coredump generated with current mt7921
> firmware. Otherwise, a truncated coredump would be reported to userland
> via dev_coredumpv.
> 
> Also, there is an additional error handling enhanced in the patch to avoid
> the possible invalid buffer access when the system failed to create the
> buffer to hold the coredump.
> 
> Fixes: 0da3c795d07b ("mt76: mt7921: add coredump support")
> Co-developed-by: YN Chen <YN.Chen at mediatek.com>
> Signed-off-by: YN Chen <YN.Chen at mediatek.com>
> Signed-off-by: Sean Wang <sean.wang at mediatek.com>
> ---
>  drivers/net/wireless/mediatek/mt76/mt76_connac.h | 2 +-
>  drivers/net/wireless/mediatek/mt76/mt7921/mac.c  | 9 ++++++---
>  2 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac.h b/drivers/net/wireless/mediatek/mt76/mt76_connac.h
> index 9b3f8d22f17e..d93ab1ece8ae 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76_connac.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt76_connac.h
> @@ -13,7 +13,7 @@
>  #define MT76_CONNAC_MAX_SCAN_MATCH		16
>  
>  #define MT76_CONNAC_COREDUMP_TIMEOUT		(HZ / 20)
> -#define MT76_CONNAC_COREDUMP_SZ			(128 * 1024)
> +#define MT76_CONNAC_COREDUMP_SZ			(1300 * 1024)
>  
>  enum {
>  	CMD_CBW_20MHZ = IEEE80211_STA_RX_BW_20,
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
> index fb4de73df701..905dddbfbb0b 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
> @@ -1557,7 +1557,7 @@ void mt7921_coredump_work(struct work_struct *work)
>  			break;
>  
>  		skb_pull(skb, sizeof(struct mt7921_mcu_rxd));
> -		if (data + skb->len - dump > MT76_CONNAC_COREDUMP_SZ) {
> +		if (!dump || data + skb->len - dump > MT76_CONNAC_COREDUMP_SZ) {

why not just return if dump allocation fails? Doing so we will reset the device
even if dump is NULL, do you think it is a real use-case?

Regards,
Lorenzo

>  			dev_kfree_skb(skb);
>  			continue;
>  		}
> @@ -1567,7 +1567,10 @@ void mt7921_coredump_work(struct work_struct *work)
>  
>  		dev_kfree_skb(skb);
>  	}
> -	dev_coredumpv(dev->mt76.dev, dump, MT76_CONNAC_COREDUMP_SZ,
> -		      GFP_KERNEL);
> +
> +	if (dump)
> +		dev_coredumpv(dev->mt76.dev, dump, MT76_CONNAC_COREDUMP_SZ,
> +			      GFP_KERNEL);
> +
>  	mt7921_reset(&dev->mt76);
>  }
> -- 
> 2.25.1
> 
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