# Re: \[PATCH net-next v5\] rust: net: netlink: validate attribute length before casting to \`c\_int\`

- From: Andrew Lunn \<andrew@lunn.ch\>
- Date: 2026-09-24 19:23:06 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/09/17638866
- Thread: https://ratatoskr.run/netdev/2026/09/17638697/t.md

```text
On Thu, Sep 24, 2026 at 06:58:25PM +0000, Sagar Taunk wrote:
> `put()` trusted an unchecked `as` cast from `usize` to `c_int`.
> When the length exceeds `i32::MAX` that cast wraps around to a
> negative value.
> 
> This ultimately resulted in a kernel panic when the reinterpreted
> value via `__nla_reserve()` and `skb_put()` became enormous.
> 
> Validate payload and header both fit together in a `u16`, rejecting
> any payload that wouldn't leave room for `NLA_HDRLEN`.
> 
> Fixes: 5eaa5fbb6e6c ("rust: netlink: add raw netlink abstraction")

Seems i was too slow giving you the link to the Documentation.

If this is a fix, and needs back porting to stable, you should base
your patch on net, not net-next.

     Andrew
```