Re: [PATCH] net: atm: lec: add pre_send validation to avoid uninitialized

[Simon Horman]

+ Edward

On Sun, Dec 07, 2025 at 04:14:53AM +0000, Dharanitharan R wrote:
> syzbot reported a KMSAN uninitialized-value crash caused by reading
> fields from struct atmlec_msg before validating that the skb contains
> enough linear data. A malformed short skb can cause lec_arp_update()
> and other handlers to access uninitialized memory.
> 
> Add a pre_send() validator that ensures the message header and optional
> TLVs are fully present. This prevents all lec message types from reading
> beyond initialized skb data.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: syzbot+5dd615f890ddada54057@xxxxxxxxxxxxxxxxxxxxxxxxx
> Tested-by: syzbot+5dd615f890ddada54057@xxxxxxxxxxxxxxxxxxxxxxxxx

No blank lines between tags please.

> 
> Closes: https://syzkaller.appspot.com/bug?extid=5dd615f890ddada54057

Likewise here.

> 
> Signed-off-by: Dharanitharan R <dharanitharan725@xxxxxxxxx>

But more importantly, this seems to duplicate another patch
that is under review:

* [PATCH net v3] net: atm: implement pre_send to check input before sending
  https://lore.kernel.org/all/tencent_4312C2065549BCEEF0EECACCA467F446F406@xxxxxx/