netdev - Re: [PATCH] memset skb to zero to avoid uninit value error from KMSAN

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Message-ID: <20251207175442.7d5ea387@pumpkin>
Date: Sun, 7 Dec 2025 17:54:42 +0000
From: David Laight <david.laight.linux@...il.com>
To: Syed Tayyab Farooq <syedtayyabfarooq08@...il.com>
Cc: netdev@...r.kernel.org,
 syzbot+0e665e4b99cb925286a0@...kaller.appspotmail.com, Syed Tayyab Farooq
 <tayyabfarooq1997@...look.com>
Subject: Re: [PATCH] memset skb to zero to avoid uninit value error from
 KMSAN

On Mon,  8 Dec 2025 00:20:52 +0800
Syed Tayyab Farooq <syedtayyabfarooq08@...il.com> wrote:

> Signed-off-by: Syed Tayyab Farooq <tayyabfarooq1997@...look.com>
> ---
> 
> Hi syzbot,
> 
> Please test this patch.
> 
> #syz test: https://syzkaller.appspot.com/bug?extid=0e665e4b99cb925286a0
> 
> Thanks,
> Tayyab
> 
> 
>  net/phonet/af_phonet.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/phonet/af_phonet.c b/net/phonet/af_phonet.c
> index a27efa4faa4e..9279decd680b 100644
> --- a/net/phonet/af_phonet.c
> +++ b/net/phonet/af_phonet.c
> @@ -208,6 +208,8 @@ static int pn_raw_send(const void *data, int len, struct net_device *dev,
>  	if (skb == NULL)
>  		return -ENOMEM;
>  
> +	memset(skb, 0, MAX_PHONET_HEADER + len);

That looks entirely broken.
Did you try running it?

	David


> +
>  	if (phonet_address_lookup(dev_net(dev), pn_addr(dst)) == 0)
>  		skb->pkt_type = PACKET_LOOPBACK;
>