Re: NULL dereference in rpcauth_lookup_credcache

["bfields@fieldses.org" <bfields@fieldses.org>]

On Mon, Nov 12, 2018 at 05:59:33PM +0000, Trond Myklebust wrote:
> On Sat, 2018-11-10 at 16:49 -0500, Bruce Fields wrote:
> > Looks like it's the fault of
> > 
> > 07d02a67b7faae "SUNRPC: Simplify lookup code"
> 
> I'm having trouble reproducing this bug. I've tried both cthon and
> xfstests in a loop, so far without success (both NFSv3 and v4.1, but
> only sec=sys). Is there anything else you're doing that I might try?
> 
> e.g. Are you running multiple workloads in parallel? Different users?..

Nothing that interesting.  Currently it's connectathon over v4, v3,
v4/krb5, v3/krb5, v4/krb5i, v4/krb5p, v4.1, v4.1/krb5, but just serially
one after the other.  Then some pynfs tests (which bypass the client),
then xfstests over v4.2/sys.  And also a few one-off locking tests of my
own that probably aren't a factor here.

(Hah, I just realized I was mounting with vers=4 and assuming that meant
4.0, but actually it's changed over time depending on the defaults, so
currently those "v4" runs are actually all 4.2.  Gah.)

--b.

> 
> > 
> > --b.
> > 
> > On Fri, Nov 09, 2018 at 01:01:30PM -0500, Chuck Lever wrote:
> > > 
> > > > On Nov 8, 2018, at 4:44 PM, J. Bruce Fields <bfields@fieldses.org
> > > > > wrote:
> > > > 
> > > > Since -rc1 my regression tests crash my client.  Is this a known
> > > > problem?  I'll investigate some more, I haven't even looked at
> > > > the code
> > > > yet or checked which test exactly is hitting this.
> > > > 
> > > > --b.
> > > > 
> > > > [  164.109570] BUG: unable to handle kernel NULL pointer
> > > > dereference at 0000000000000008
> > > > [  164.111207] PGD 0 P4D 0 
> > > > [  164.111528] Oops: 0000 [#1] PREEMPT SMP PTI
> > > > [  164.112303] CPU: 2 PID: 2947 Comm: kworker/u8:5 Not tainted
> > > > 4.20.0-rc1-13223-gafb6d1c474ef #1898
> > > > [  164.113487] Hardware name: QEMU Standard PC (i440FX + PIIX,
> > > > 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fedoraproject.org-
> > > > 1.fc28 04/01/2014
> > > > [  164.115301] Workqueue: rpciod rpc_async_schedule [sunrpc]
> > > > [  164.115920] RIP: 0010:rpcauth_lookup_credcache+0x3d/0x450
> > > > [sunrpc]
> > > > [  164.116700] Code: 89 f5 41 54 41 89 d4 53 48 83 ec 38 89 4d b0
> > > > 4c 8b 7f 20 65 48 8b 04 25 28 00 00 00 48 89 45 d0 31 c0 48 8d 45
> > > > c0 48 89 45 c8 <41> 8b 77 08 48 89 45 c0 48 8b 47 10 4c 89 ef 48
> > > > 8b 40 28 e8 cb d2
> > > > [  164.119299] RSP: 0018:ffffc90001ee3cf0 EFLAGS: 00010246
> > > > [  164.119872] RAX: ffffc90001ee3d10 RBX: ffff88007cc18180 RCX:
> > > > 0000000000600040
> > > > [  164.120800] RDX: 0000000000000001 RSI: ffffc90001ee3d60 RDI:
> > > > ffff88007cafb198
> > > > [  164.121643] RBP: ffffc90001ee3d50 R08: 0000000000000000 R09:
> > > > 0000000000000000
> > > > [  164.122464] R10: 0000000000000000 R11: 0000000000000000 R12:
> > > > 0000000000000001
> > > > [  164.123373] R13: ffffc90001ee3d60 R14: ffff88007cafb198 R15:
> > > > 0000000000000000
> > > > [  164.124296] FS:  0000000000000000(0000)
> > > > GS:ffff88007fd00000(0000) knlGS:0000000000000000
> > > > [  164.125322] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > [  164.126006] CR2: 0000000000000008 CR3: 000000007829c003 CR4:
> > > > 00000000001606e0
> > > > [  164.126860] Call Trace:
> > > > [  164.127045]  ? call_retry_reserve+0x30/0x30 [sunrpc]
> > > > [  164.127622]  rpcauth_lookupcred+0xa0/0xc0 [sunrpc]
> > > > [  164.128200]  rpcauth_refreshcred+0x15f/0x170 [sunrpc]
> > > > [  164.128807]  __rpc_execute+0xa9/0x460 [sunrpc]
> > > > [  164.129281]  process_one_work+0x227/0x630
> > > > [  164.129684]  worker_thread+0x3c/0x390
> > > > [  164.130062]  ? process_one_work+0x630/0x630
> > > > [  164.130609]  kthread+0x11d/0x140
> > > > [  164.130936]  ? kthread_park+0x80/0x80
> > > > [  164.131339]  ret_from_fork+0x3a/0x50
> > > > [  164.131676] Modules linked in: rpcsec_gss_krb5 nfsv4 nfs lockd
> > > > grace auth_rpcgss sunrpc
> > > > [  164.132719] CR2: 0000000000000008
> > > > [  164.133050] ---[ end trace b4028a6781a696ad ]---
> > > > 
> > > 
> > > I just encountered this repeatedly with cthon04 general tests.
> > > 
> > > MNTOPTIONS="rw,proto=tcp,vers=4.1,sec=sys"
> > > 
> > > 
> > > --
> > > Chuck Lever
> > > chucklever@gmail.com
> > > 
> > > 
> -- 
> Trond Myklebust
> CTO, Hammerspace Inc
> 4300 El Camino Real, Suite 105
> Los Altos, CA 94022
> www.hammer.space
> 
>