On Fri, 2019-05-24 at 15:22 -0400, Olga Kornievskaia wrote:
> From: Olga Kornievskaia <kolga@xxxxxxxxxx>
>
> It's possible that on an umount we send a NULL call to destroy
> a gss context and a failure occurs on the reply. Since it's possible
> that in that case the rpc client and auth structure are going away
> don't retry. Otherwise, the kernel hits the following oops.
>
> [37247.291617] BUG: unable to handle kernel NULL pointer dereference
> at 0000000000000098
> [37247.296200] #PF error: [normal kernel read fault]
> [37247.298110] PGD 0 P4D 0
> [37247.299264] Oops: 0000 [#1] SMP PTI
> [37247.300729] CPU: 1 PID: 23870 Comm: kworker/u256:1 Not tainted
> 5.1.0+ #172
> [37247.303547] Hardware name: VMware, Inc. VMware Virtual
> Platform/440BX Desktop Reference Platform, BIOS 6.00 04/13/2018
> [37247.311770] Workqueue: rpciod rpc_async_schedule [sunrpc]
> [37247.313958] RIP: 0010:xprt_adjust_timeout+0x9/0x110 [sunrpc]
> [37247.316220] Code: c7 c7 20 0d 50 c0 31 c0 e8 68 00 e2 fc 41 c7 45
> 04 f4 ff ff ff eb c9 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41
> 54 55 53 <48> 8b 87 98 00 00 00 48 89 fb 4c 8b 27 48 8b 80 a8 00 00
> 00
> 48 8b
> [37247.323625] RSP: 0018:ffffb0ab84f5fd68 EFLAGS: 00010207
> [37247.325676] RAX: 00000000fffffff5 RBX: ffff9e0ff1042800 RCX:
> 0000000000000003
> [37247.328433] RDX: ffff9e0ff11baac0 RSI: 00000000fffffe01 RDI:
> 0000000000000000
> [37247.331206] RBP: ffff9e0fe20cb200 R08: ffff9e0ff11baac0 R09:
> ffff9e0ff11baac0
> [37247.334038] R10: ffff9e0ff11baab8 R11: 0000000000000003 R12:
> ffff9e1039b55050
> [37247.337098] R13: ffff9e0ff1042830 R14: 0000000000000000 R15:
> 0000000000000001
> [37247.339966] FS: 0000000000000000(0000) GS:ffff9e103bc40000(0000)
> knlGS:0000000000000000
> [37247.343261] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [37247.345669] CR2: 0000000000000098 CR3: 000000007603a002 CR4:
> 00000000001606e0
> [37247.348564] Call Trace:
> [37247.351034] rpc_check_timeout+0x1d/0x140 [sunrpc]
> [37247.353005] call_decode+0x13e/0x1f0 [sunrpc]
> [37247.354893] ? rpc_check_timeout+0x140/0x140 [sunrpc]
> [37247.357143] __rpc_execute+0x7e/0x3d0 [sunrpc]
> [37247.359104] rpc_async_schedule+0x29/0x40 [sunrpc]
> [37247.362565] process_one_work+0x16b/0x370
> [37247.365598] worker_thread+0x49/0x3f0
> [37247.367164] kthread+0xf5/0x130
> [37247.368453] ? max_active_store+0x80/0x80
> [37247.370087] ? kthread_bind+0x10/0x10
> [37247.372505] ret_from_fork+0x1f/0x30
> [37247.374695] Modules linked in: nfsv3 cts rpcsec_gss_krb5 nfsv4
> dns_resolver nfs rfcomm fuse ip6t_rpfilter ipt_REJECT nf_reject_ipv4
> ip6t_REJECT nf_reject_ipv6 xt_conntrack nf_conntrack nf_defrag_ipv6
> nf_defrag_ipv4 ebtable_nat ebtable_broute bridge stp llc
> ip6table_mangle ip6table_security ip6table_raw iptable_mangle
> iptable_security iptable_raw ebtable_filter ebtables ip6table_filter
> ip6_tables iptable_filter bnep snd_seq_midi snd_seq_midi_event
> crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel
> crypto_simd cryptd glue_helper vmw_balloon snd_ens1371 snd_ac97_codec
> uvcvideo ac97_bus snd_seq pcspkr btusb btrtl btbcm videobuf2_vmalloc
> snd_pcm videobuf2_memops btintel videobuf2_v4l2 videodev bluetooth
> snd_timer snd_rawmidi vmw_vmci snd_seq_device rfkill videobuf2_common
> snd ecdh_generic i2c_piix4 soundcore nfsd nfs_acl lockd auth_rpcgss
> grace sunrpc ip_tables xfs libcrc32c sr_mod cdrom sd_mod ata_generic
> pata_acpi vmwgfx drm_kms_helper syscopyarea sysfillrect sysimgblt
> fb_sys_fops
> [37247.389774] ttm crc32c_intel drm serio_raw ahci ata_piix libahci
> libata mptspi scsi_transport_spi e1000 mptscsih mptbase i2c_core
> dm_mirror dm_region_hash dm_log dm_mod
> [37247.437859] CR2: 0000000000000098
> [37247.462263] ---[ end trace 0d9a85f0df2cef9e ]---
>
> Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
> ---
> net/sunrpc/clnt.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index 8ff11dc..8928f93 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -2487,7 +2487,7 @@ void rpc_force_rebind(struct rpc_clnt *clnt)
>
> out_garbage:
> clnt->cl_stats->rpcgarbage++;
> - if (task->tk_garb_retry) {
> + if (task->tk_garb_retry && !(task->tk_flags & RPC_TASK_KILLED))
> {
> task->tk_garb_retry--;
> task->tk_action = call_encode;
> return -EAGAIN;
> @@ -2541,7 +2541,7 @@ void rpc_force_rebind(struct rpc_clnt *clnt)
> case rpc_autherr_badcred:
> case rpc_autherr_badverf:
> /* possibly garbled cred/verf? */
> - if (!task->tk_garb_retry)
> + if (!task->tk_garb_retry || task->tk_flags &
> RPC_TASK_KILLED)
> break;
> task->tk_garb_retry--;
> trace_rpc__bad_creds(task);
Hmm... The RPC_TASK_KILLED flag was changed in 5.2-rc1 in order to try
to fix a few atomicity issues with it, so the above patch will not
apply to the current codebase.
The new behaviour will actually check the new flag in __rpc_execute()
itself (see the check of RPC_SIGNALLED()). I'd therefore be very
interested to see if the bug is still reproducible with the newest 5.2-
rcX.
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
