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From: David Howells <dhowells@redhat.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: dhowells@redhat.com, Jakub Kicinski <kuba@kernel.org>,
	syzbot <syzbot+f527b971b4bdc8e79f9e@syzkaller.appspotmail.com>,
	bpf@vger.kernel.org, brauner@kernel.org, davem@davemloft.net,
	dsahern@kernel.org, edumazet@google.com,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, pabeni@redhat.com,
	syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk
Subject: Re: Endless loop in udp with MSG_SPLICE_READ - Re: [syzbot] [fs?] INFO: task hung in pipe_release (4)
Date: Mon, 31 Jul 2023 14:34:01 +0100	[thread overview]
Message-ID: <1125142.1690810441@warthog.procyon.org.uk> (raw)
In-Reply-To: <64c7acd57270c_169cd129420@willemb.c.googlers.com.notmuch>

Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote:

> Is the MSG_CONFIRM needed to trigger this?

It's not actually necessary.  The syz test was doing it.

> Is this indeed trivially sidestepped if downgrading from splicing to
> regular copying with fragmentation?

That works.  The logging looks like:

==>splice_to_socket() 5535
udp_sendmsg(8,8)
__ip_append_data(copy=-1,len=8, mtu=8192 skblen=8189 maxfl=8188)
copy 8 = 9 - 0 - 1 - 0
length 8 -= 8 + 0
<==splice_to_socket() = 8

It looks like pagedlen being non-zero might be the issue.

David


  parent reply	other threads:[~2023-07-31 13:35 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-12  7:35 syzbot
2023-07-12 18:54 ` syzbot
2023-07-18 23:07   ` Jakub Kicinski
2023-07-24 13:17   ` David Howells
2023-07-28 23:52   ` David Howells
2023-07-29 15:27   ` David Howells
2023-07-29 21:49   ` Endless loop in udp with MSG_SPLICE_READ - " David Howells
2023-07-30 13:35     ` Willem de Bruijn
2023-07-30 14:30       ` Willem de Bruijn
2023-07-30 17:32     ` David Howells
2023-07-31  8:13     ` David Howells
2023-07-31 12:45       ` Willem de Bruijn
2023-07-31 13:34       ` David Howells [this message]
2023-08-01 12:40       ` David Howells
2023-08-01 12:58         ` Willem de Bruijn
2023-08-01 13:08         ` Willem de Bruijn
2023-08-01 14:01         ` David Howells
2023-08-01 14:02         ` David Howells
2023-08-01 14:19         ` David Howells
2023-08-01 14:31           ` Willem de Bruijn
2023-08-01 14:47           ` David Howells
2023-08-01 14:59             ` Willem de Bruijn
2023-08-02 13:21   ` David Howells
2023-08-02 16:48     ` syzbot

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