Subject: Re: [PATCH net] vsock/virtio: fix skb overhead overflow on 32-bit builds

From: David Laight <[email-masked]>
Date: Sat, 23 May 2026 17:35:57 +0100

On Sat, 23 May 2026 02:20:29 +0000
[email-masked] wrote:

> Hello:
> 
> This patch was applied to netdev/net.git (main)
> by Jakub Kicinski <[email-masked]>:

Did anyone else notice that is isn't a bug?

There is no way that a 'count of bytes of kernel memory' can overflow
the size of 'long'.

-- David
 
> 
> On Thu, 21 May 2026 14:47:32 +0200 you wrote:
> > From: Stefano Garzarella <[email-masked]>
> > 
> > On 32-bit architectures, both skb_queue_len() and SKB_TRUESIZE(0) evaluate
> > to 32-bit values. The multiplication can overflow before being assigned to
> > the u64 skb_overhead variable, making the skb overhead check ineffective.
> > 
> > Cast skb_queue_len() to u64 so the multiplication is always performed in
> > 64-bit arithmetic.
> > 
> > [...]  
> 
> Here is the summary with links:
>   - [net] vsock/virtio: fix skb overhead overflow on 32-bit builds
>     https://git.kernel.org/netdev/net/c/4157501b9a8f
> 
> You are awesome, thank you!