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Date:   Tue, 12 Nov 2019 13:57:48 -0500
From:   Scott Mayhew <smayhew@redhat.com>
To:     "J. Bruce Fields" <bfields@redhat.com>, linux-nfs@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: PROBLEM: NULL pointer dereference; nfsd4_remove_cld_pipe
Message-ID: <20191112185748.GG4276@coeurl.usersys.redhat.com>
References: <20191112101343.GA2806@audible.transient.net>
 <20191112162047.GF4276@coeurl.usersys.redhat.com>
 <20191112181309.GA2776@audible.transient.net>
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On Tue, 12 Nov 2019, Jamie Heilman wrote:

> Scott Mayhew wrote:
> > Hi Jamie,
> >=20
> > On Tue, 12 Nov 2019, Jamie Heilman wrote:
> >=20
> > > Giving 5.4.0-rc7 a spin I hit a NULL pointer dereference and bisected
> > > it to:
> > >=20
> > > commit 6ee95d1c899186c0798cafd25998d436bcdb9618
> > > Author: Scott Mayhew <smayhew@redhat.com>
> > > Date:   Mon Sep 9 16:10:31 2019 -0400
> > >=20
> > >     nfsd: add support for upcall version 2
> > >=20
> > >=20
> > > The splat against 5.3.0-rc2-00034-g6ee95d1c8991:
> > >=20
> > > BUG: kernel NULL pointer dereference, address: 0000000000000036
> > > #PF: supervisor read access in kernel mode
> > > #PF: error_code(0x0000) - not-present page
> > > PGD 0 P4D 0=20
> > > Oops: 0000 [#1] PREEMPT SMP PTI
> > > CPU: 0 PID: 2936 Comm: rpc.nfsd Not tainted 5.3.0-rc2-00034-g6ee95d1c=
8991 #1
> > > Hardware name: Dell Inc. Precision WorkStation T3400  /0TP412, BIOS A=
14 04/30/2012
> > > RIP: 0010:crypto_destroy_tfm+0x5/0x4d
> > > Code: 78 01 00 00 48 85 c0 74 05 e9 05 05 66 00 c3 55 48 8b af 80 01 =
00 00 e8 d5 ff ff ff 48 89 ef 5d e9 12 f9 ef ff 48 85 ff 74 47 <48> 83 7e 3=
0 00 41 55 4c 8b 6e 38 41 54 49 89 fc 55 48 89 f5 75 14
> > > RSP: 0018:ffffc90000b7bd68 EFLAGS: 00010282
> > > RAX: ffffffffa0402841 RBX: ffff888230484400 RCX: 0000000000002cd0
> > > RDX: 0000000000002cce RSI: 0000000000000006 RDI: fffffffffffffffe
> > > RBP: ffffffff81e68440 R08: ffff888232801800 R09: ffffffffa0402841
> > > R10: 0000000000000200 R11: ffff88823048ae40 R12: ffff888231585100
> > > R13: ffff88823048ae40 R14: 000000000000000b R15: ffff888230484400
> > > FS:  00007f02102c3740(0000) GS:ffff888233a00000(0000) knlGS:000000000=
0000000
> > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 0000000000000036 CR3: 0000000230f94000 CR4: 00000000000406f0
> > > Call Trace:
> > >  nfsd4_remove_cld_pipe+0x6d/0x83 [nfsd]
> > >  nfsd4_cld_tracking_init+0x1cf/0x295 [nfsd]
> > >  nfsd4_client_tracking_init+0x72/0x13e [nfsd]
> > >  nfs4_state_start_net+0x22a/0x2cf [nfsd]
> > >  nfsd_svc+0x1c6/0x292 [nfsd]
> > >  write_threads+0x68/0xb0 [nfsd]
> > >  ? write_versions+0x333/0x333 [nfsd]
> > >  nfsctl_transaction_write+0x4a/0x62 [nfsd]
> > >  vfs_write+0xa0/0xdd
> > >  ksys_write+0x71/0xba
> > >  do_syscall_64+0x48/0x55
> > >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > > RIP: 0033:0x7f021056c904
> > > Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 =
00 48 8d 05 d9 3a 0d 00 8b 00 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f=
0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 48 89 54 24 18 48
> > > RSP: 002b:00007ffdc76ec618 EFLAGS: 00000246 ORIG_RAX: 000000000000000=
1
> > > RAX: ffffffffffffffda RBX: 000055b534955560 RCX: 00007f021056c904
> > > RDX: 0000000000000002 RSI: 000055b534955560 RDI: 0000000000000003
> > > RBP: 0000000000000003 R08: 0000000000000000 R09: 00007ffdc76ec4b0
> > > R10: 00007ffdc76ec367 R11: 0000000000000246 R12: 0000000000000000
> > > R13: 0000000000000008 R14: 0000000000000000 R15: 000055b534b8a2a0
> > > Modules linked in: cpufreq_userspace cpufreq_powersave cpufreq_ondema=
nd cpufreq_conservative autofs4 fan nfsd auth_rpcgss nfs lockd grace fscach=
e sunrpc bridge stp llc nhpoly1305_sse2 nhpoly1305 aes_generic chacha_x86_6=
4 chacha_generic adiantum poly1305_generic vhost_net tun vhost tap dm_crypt=
 snd_hda_codec_analog snd_hda_codec_generic usb_storage snd_hda_intel kvm_i=
ntel snd_hda_codec kvm snd_hwdep snd_hda_core snd_pcm dcdbas snd_timer irqb=
ypass snd soundcore sr_mod cdrom tg3 sg floppy evdev xfs dm_mod raid1 md_mo=
d psmouse
> > > CR2: 0000000000000036
> > > ---[ end trace bc12bbe4cdd6319f ]---
> > > ...
> > > NFS: Registering the id_resolver key type
> > > Key type id_resolver registered
> > > Key type id_legacy registered
> > >=20
> > >=20
> > > My kernel config is at
> > > http://audible.transient.net/~jamie/k/upcallv2.config-5.3.0-rc2-00034=
-g6ee95d1c8991
> > >=20
> > > I don't think there's anything terribly interesting about my nfs
> > > server setup, this happens reliably on boot up, idle network, no
> > > active clients; let me know what else you need, happy to debug.
> > >=20
> > > --=20
> > > Jamie Heilman                     http://audible.transient.net/~jamie=
/
> > >=20
> > Please try this patch (v2 because I messed up the first one).
>=20
>=20
> Yep, that seems to solve it.=20

Thanks!  There's another small problem, in that nfsd could incorrectly
fall back to using the old nfsdcld tracking ops even if nfsdcld isn't
running... so a v3 patch is forthcoming.

> Is the implication that
> CONFIG_CRYPTO_SHA256 should be selected by nfsd?  (I tested with it
> unset, as per my config before.)

Yes - I'll send a separate patch for that.

-Scott
>=20
>=20
> --=20
> Jamie Heilman                     http://audible.transient.net/~jamie/
>=20