linux-kernel - Re: WARN_ON(fuse_insert_writeback(root, wpa)) in tree

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Message-ID: <CAJfpegv4jLewQ4G_GdxraTE8fGHy7-d52gPSi4ZAOp0N4aYJnw@mail.gmail.com>
Date:   Thu, 29 Oct 2020 16:20:55 +0100
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Qian Cai <cai@...hat.com>
Cc:     Vivek Goyal <vgoyal@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        virtio-fs-list <virtio-fs@...hat.com>
Subject: Re: WARN_ON(fuse_insert_writeback(root, wpa)) in tree_insert()

On Thu, Oct 29, 2020 at 4:02 PM Qian Cai <cai@...hat.com> wrote:
>
> On Wed, 2020-10-07 at 16:08 -0400, Qian Cai wrote:
> > Running some fuzzing by a unprivileged user on virtiofs could trigger the
> > warning below. The warning was introduced not long ago by the commit
> > c146024ec44c ("fuse: fix warning in tree_insert() and clean up writepage
> > insertion").
> >
> > From the logs, the last piece of the fuzzing code is:
> >
> > fgetxattr(fd=426, name=0x7f39a69af000, value=0x7f39a8abf000, size=1)
>
> I can still reproduce it on today's linux-next. Any idea on how to debug it
> further?

Can you please try the attached patch?

Thanks,
Miklos

View attachment "fuse-launder-page-should-wait-for-page-writeback.patch" of type "text/x-patch" (515 bytes)