[PATCH] nfsd4: Fix NULL dereference in legacy_recdir_name_error()

[Takashi Iwai]

The recent rewrite of NFSv4 recovery client tracking options per net
(commit 9a9c6478) introduced Oops when it faces an error for recdir
generation.

  NFSD: unable to generate recoverydir name (-2).
  NFSD: disabling legacy clientid tracking. Reboot recovery will not function correctly!
  BUG: unable to handle kernel NULL pointer dereference at 00000000000007a8
  IP: [<ffffffffa060c6c7>] nfsd4_client_tracking_exit+0x17/0x70 [nfsd]
  PGD 0
  Oops: 0000 [#1] PREEMPT SMP
  Modules linked in: nfsd fuse nfsv3 nfs_acl nfsv4 auth_rpcgss nfs lockd sunrpc cpufreq_conservative cpufreq_userspace cpufreq_powersave snd_hda_codec_hdmi snd_hda_codec_realtek intel_powerclamp acpi_cpufreq mperf coretemp ghash_clmulni_intel aesni_intel kvm_intel snd_hda_intel ablk_helper snd_hda_codec snd_hwdep kvm snd_pcm cryptd lrw aes_x86_64 snd_timer xts gf128mul e1000e snd sr_mod iTCO_wdt microcode cdrom usb_storage dcdbas iTCO_vendor_support i2c_i801 cdc_acm sg ptp lpc_ich mei soundcore pps_core mfd_core snd_page_alloc pciehp pci_hotplug autofs4 btrfs raid6_pq zlib_deflate xor libcrc32c i915 crc32c_intel drm_kms_helper drm xhci_hcd i2c_algo_bit thermal button video processor thermal_sys scsi_dh_rdac scsi_dh_hp_sw scsi_dh_emc scsi_dh_alua scsi_dh
  CPU 1
  Pid: 19567, comm: nfsd Not tainted 3.9.0-rc5-test+ #3 Dell Inc. OptiPlex 9010/0M9KCM
  RIP: 0010:[<ffffffffa060c6c7>]  [<ffffffffa060c6c7>] nfsd4_client_tracking_exit+0x17/0x70 [nfsd]
  RSP: 0018:ffff880181099c28  EFLAGS: 00010202
  RAX: ffff8801810900c0 RBX: 0000000000000004 RCX: 0000000000000006
  RDX: 0000000000000007 RSI: 0000000000000046 RDI: 0000000000000000
  RBP: ffff880181099c38 R08: 000000000000000a R09: 000000000000039f
  R10: 0000000000000000 R11: 000000000000039e R12: 0000000000000000
  R13: ffffffff81a87280 R14: ffff88014c819220 R15: ffff88020b75d200
  FS:  0000000000000000(0000) GS:ffff88021e240000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00000000000007a8 CR3: 0000000001a0d000 CR4: 00000000001407e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
  Process nfsd (pid: 19567, threadinfo ffff880181098000, task ffff8801810900c0)
  Stack:
   00000000fffffffe ffff88020b75d200 ffff880181099c58 ffffffffa060c75c
   ffffffff81a87280 ffff880002ba7000 ffff880181099cc8 ffffffffa060cb37
   ffff880181099d20 ffff88014c819220 0000000000000001 ffff88020b75d200
  Call Trace:
   [<ffffffffa060c75c>] legacy_recdir_name_error+0x3c/0x40 [nfsd]
   [<ffffffffa060cb37>] nfsd4_create_clid_dir+0xe7/0x200 [nfsd]
   [<ffffffffa0600323>] ? nfs4_preprocess_seqid_op+0x63/0x160 [nfsd]
   [<ffffffffa060ccaf>] nfsd4_client_record_create+0x5f/0x80 [nfsd]
   [<ffffffffa0604eef>] nfsd4_open_confirm+0x12f/0x1b0 [nfsd]
   [<ffffffffa05f35cf>] nfsd4_proc_compound+0x55f/0x770 [nfsd]
   [<ffffffffa05e0ded>] nfsd_dispatch+0xdd/0x220 [nfsd]
   [<ffffffffa04e58b8>] svc_process_common+0x328/0x6d0 [sunrpc]
   [<ffffffffa04e5fbc>] svc_process+0x10c/0x160 [sunrpc]
   [<ffffffffa05e079f>] nfsd+0xbf/0x130 [nfsd]
   [<ffffffffa05e06e0>] ? nfsd_destroy+0x90/0x90 [nfsd]
   [<ffffffff8106a4cb>] kthread+0xbb/0xc0
   [<ffffffff8106a410>] ? kthread_create_on_node+0x130/0x130
   [<ffffffff815b373c>] ret_from_fork+0x7c/0xb0
   [<ffffffff8106a410>] ? kthread_create_on_node+0x130/0x130
  Code: e0 49 8b 84 24 48 01 00 00 e9 25 ff ff ff 66 0f 1f 44 00 00 55 48 89 e5 41 54 49 89 fc 53 8b 1d 44 b4 00 00 e8 bb a9 a5 e0 85 db <49> 8b 84 24 a8 07 00 00 74 43 3b 18 77 3f 83 eb 01 48 63 db 48
  RIP  [<ffffffffa060c6c7>] nfsd4_client_tracking_exit+0x17/0x70 [nfsd]
   RSP <ffff880181099c28>
  CR2: 00000000000007a8
  ---[ end trace 5dd4307598e98cef ]---

This patch fixes it by passing the proper net instance instead of
NULL.

Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [v3.8+]
---
 fs/nfsd/nfs4recover.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 899ca26..ae0d5c9 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -146,7 +146,7 @@ out_no_tfm:
  * then disable recovery tracking.
  */
 static void
-legacy_recdir_name_error(int error)
+legacy_recdir_name_error(struct net *net, int error)
 {
 	printk(KERN_ERR "NFSD: unable to generate recoverydir "
 			"name (%d).\n", error);
@@ -160,8 +160,7 @@ legacy_recdir_name_error(int error)
 		printk(KERN_ERR "NFSD: disabling legacy clientid tracking. "
 			"Reboot recovery will not function correctly!\n");
 
-		/* the argument is ignored by the legacy exit function */
-		nfsd4_client_tracking_exit(NULL);
+		nfsd4_client_tracking_exit(net);
 	}
 }
 
@@ -184,7 +183,7 @@ nfsd4_create_clid_dir(struct nfs4_client *clp)
 
 	status = nfs4_make_rec_clidname(dname, &clp->cl_name);
 	if (status)
-		return legacy_recdir_name_error(status);
+		return legacy_recdir_name_error(clp->net, status);
 
 	status = nfs4_save_creds(&original_cred);
 	if (status < 0)
@@ -341,7 +340,7 @@ nfsd4_remove_clid_dir(struct nfs4_client *clp)
 
 	status = nfs4_make_rec_clidname(dname, &clp->cl_name);
 	if (status)
-		return legacy_recdir_name_error(status);
+		return legacy_recdir_name_error(clp->net, status);
 
 	status = mnt_want_write_file(nn->rec_file);
 	if (status)
@@ -601,7 +600,7 @@ nfsd4_check_legacy_client(struct nfs4_client *clp)
 
 	status = nfs4_make_rec_clidname(dname, &clp->cl_name);
 	if (status) {
-		legacy_recdir_name_error(status);
+		legacy_recdir_name_error(clp->net, status);
 		return status;
 	}
 
-- 
1.8.1.4

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