Re: Endless loop in udp with MSG_SPLICE_READ - Re: [syzbot] [fs?] INFO: task hung in pipe_release (4)

[David Howells]

Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx> 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