netdev - Re: [PATCH net v2] netlink: Add string check in netlink_ack_tlv

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Message-ID: <20241113182511.41960cc0@kernel.org>
Date: Wed, 13 Nov 2024 18:25:11 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Manas via B4 Relay <devnull+manas18244.iiitd.ac.in@...nel.org>
Cc: manas18244@...td.ac.in, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon
 Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>, Shuah
 Khan <shuah@...nel.org>, Anup Sharma <anupnewsmail@...il.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzbot+d4373fa8042c06cefa84@...kaller.appspotmail.com
Subject: Re: [PATCH net v2] netlink: Add string check in
 netlink_ack_tlv_fill

On Thu, 14 Nov 2024 06:15:15 +0530 Manas via B4 Relay wrote:
> -	if (extack->bad_attr &&
> +	if (extack->bad_attr && strlen(in_skb->data) &&
>  	    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
>  		     (u8 *)extack->bad_attr >= in_skb->data + in_skb->len))

that's most definitely not the right fix.
in_skb->data points to binary data.

my best idea so far is to rework this check to use nlh, because in_skb
will be pulled at this stage for dumps
if that makes sense to you please give it a go, otherwise I'll work on
the fix tomorrow