Re: [Syzkaller & bisect] There is BUG: unable to handle kernel NULL pointer dereference in xfs_extent_free_diff_items in v6.4-rc3

Eric Biggers
2023-05-23T00:25:03Z

On Mon, May 22, 2023 at 09:05:25AM -0700, Darrick J. Wong wrote:
> On Mon, May 22, 2023 at 01:39:27PM +0700, Bagas Sanjaya wrote:
> > On Mon, May 22, 2023 at 10:07:28AM +0800, Pengfei Xu wrote:
> > > Hi Darrick,
> > >
> > > Greeting!
> > > There is BUG: unable to handle kernel NULL pointer dereference in
> > > xfs_extent_free_diff_items in v6.4-rc3:
> > >
> > > Above issue could be reproduced in v6.4-rc3 and v6.4-rc2 kernel in guest.
> > >
> > > Bisected this issue between v6.4-rc2 and v5.11, found the problem commit is:
> > > "
> > > f6b384631e1e xfs: give xfs_extfree_intent its own perag reference
> > > "
> > >
> > > report0, repro.stat and so on detailed info is link: https://github.com/xupengfe/syzkaller_logs/tree/main/230521_043336_xfs_extent_free_diff_items
> > > Syzkaller reproduced code: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/repro.c
> > > Syzkaller reproduced prog: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/repro.prog
> > > Kconfig: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/kconfig_origin
> > > Bisect info: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/bisect_info.log
> > > Issue dmesg: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/v6.4-rc3_reproduce_dmesg.log
> > >
> > > v6.4-rc3 reproduced info:
>
> Diagnosis and patches welcomed.
>
> Or are we doing the usual syzbot bullshit where you all assume that I'm
> going to do all the fucking work for you?
>

It looks like Pengfei already took the time to manually bisect this issue to a
very recent commit authored by you. Is that not helpful?

(Apologies if I didn't include enough profanities for this email to be suitable
for linux-xfs@.)

- Eric