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Date: Wed, 13 Nov 2024 18:25:11 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Manas via B4 Relay <devnull+manas18244.iiitd.ac.in@kernel.org>
Cc: manas18244@iiitd.ac.in, "David S. Miller" <davem@davemloft.net>, Eric
 Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Simon
 Horman <horms@kernel.org>, Kuniyuki Iwashima <kuniyu@amazon.com>, Shuah
 Khan <shuah@kernel.org>, Anup Sharma <anupnewsmail@gmail.com>,
 netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
 syzbot+d4373fa8042c06cefa84@syzkaller.appspotmail.com
Subject: Re: [PATCH net v2] netlink: Add string check in
 netlink_ack_tlv_fill
Message-ID: <20241113182511.41960cc0@kernel.org>
In-Reply-To: <20241114-fix-netlink_ack_tlv_fill-v2-1-affdfb5f4c6f@iiitd.ac.in>
References: <20241114-fix-netlink_ack_tlv_fill-v2-1-affdfb5f4c6f@iiitd.ac.in>
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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