linux-kernel - Re: [PATCH Next V2] net: restore the iterator to its original state when an error occurs

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Message-ID: <tencent_7B73E6D013636363696CC3A34444F77AF705@qq.com>
Date: Mon,  1 Dec 2025 11:41:07 +0800
From: Edward Adam Davis <eadavis@...com>
To: kuba@...nel.org
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Subject: Re: [PATCH Next V2] net: restore the iterator to its original state when an error occurs

On Fri, 28 Nov 2025 09:39:46 -0800, Jakub Kicinski wrote:
> > In zerocopy_fill_skb_from_iter(), if two copy operations are performed
> > and the first one succeeds while the second one fails, it returns a
> > failure but the count in iterator has already been decremented due to
> > the first successful copy. This ultimately affects the local variable
> > rest_len in virtio_transport_send_pkt_info(), causing the remaining
> > count in rest_len to be greater than the actual iterator count. As a
> > result, packet sending operations continue even when the iterator count
> > is zero, which further leads to skb->len being 0 and triggers the warning
> > reported by syzbot [1].
> 
> Please follow the subsystem guidelines for posting patches:
> https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
> Your patch breaks zerocopy tests.
I see that they all timed out. I'm not familiar with this test, how can
I get more details about it?