kernel panic in 5.3-rc5, nfsd_reply_cache_stats_show+0x11

[jane . chu]

Hi,

Apology if there is a better channel reporting the issue, if so, please 
let me know.

I just saw below regression in 5.3-rc5 kernel, but not in 5.2-rc7 or 
earlier kernels.

[ 3533.659787] mce: Uncorrected hardware memory error in user-access at 
383e202000
[ 3533.659903] Memory failure: 0x383e202: Sending SIGBUS to 
read_poison:14493 due to hardware memory corruption
[ 3533.679041] Memory failure: 0x383e202: recovery action for dax page: 
Recovered
[ 3564.624934] BUG: kernel NULL pointer dereference, address: 
00000000000001f9
[ 3564.632707] #PF: supervisor read access in kernel mode
[ 3564.638440] #PF: error_code(0x0000) - not-present page
[ 3564.644174] PGD acd7b47067 P4D acd7b47067 PUD acd7aba067 PMD 0
[ 3564.650784] Oops: 0000 [#1] SMP NOPTI
[ 3564.654869] CPU: 58 PID: 15026 Comm: sosreport Tainted: G   M 
     5.3.0-rc5.master.20190820.ol7.x86_64 #1
[ 3564.666420] Hardware name: Oracle Corporation ORACLE SERVER 
X8-2L/ASM,MTHRBD,2U, BIOS 52020101 05/07/2019
[ 3564.677112] RIP: 0010:nfsd_reply_cache_stats_show+0x11/0x110 [nfsd]
[ 3564.684106] Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 63 
47 ec 48 89 e5 5d c3 90 0f 1f 44 00 00 55 31 c0 48 89 e5 41 54 49 89 f4 
53 <8b> 96 f8 01 00 00 48 c7 c6 d9 b8 74 c0 48 89 fb e8 9a ae bc f2 41
[ 3564.705062] RSP: 0018:ffffaa140f87fe18 EFLAGS: 00010246
[ 3564.710894] RAX: 0000000000000000 RBX: ffff9f7c9b562ca8 RCX: 
0000000000005c19
[ 3564.718858] RDX: 0000000000001000 RSI: 0000000000000001 RDI: 
ffff9f7c9b562c80
[ 3564.726822] RBP: ffffaa140f87fe28 R08: ffff9f801fab01a0 R09: 
ffff9ed347c06600
[ 3564.734785] R10: ffff9f801e287000 R11: ffff9f8012f8d638 R12: 
0000000000000001
[ 3564.742749] R13: ffff9f8012f8d600 R14: ffff9f7c9b562c80 R15: 
0000000000000001
[ 3564.750712] FS:  00007f3cfaa92700(0000) GS:ffff9f801fa80000(0000) 
knlGS:0000000000000000
[ 3564.759743] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3564.766156] CR2: 00000000000001f9 CR3: 000000add1894004 CR4: 
00000000007606e0
[ 3564.774120] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
0000000000000000
[ 3564.782084] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
0000000000000400
[ 3564.790050] PKRU: 55555554
[ 3564.793068] Call Trace:
[ 3564.795800]  seq_read+0x13b/0x390
[ 3564.799502]  __vfs_read+0x1b/0x40
[ 3564.803202]  vfs_read+0x8e/0x140
[ 3564.806794]  ksys_read+0x61/0xd0
[ 3564.810394]  __x64_sys_read+0x1a/0x20
[ 3564.814484]  do_syscall_64+0x60/0x1e0
[ 3564.818572]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 3564.824199] RIP: 0033:0x7f3d163a304d


The panic is reproducible every time in 5.3-rc5, here is the steps.

On system with Intel DC PMEM, configure at AppDirect NonInterleave mode,
# ndctl create-namespace -m devdax
{
  "dev":"namespace1.0",
  "mode":"devdax",
  "map":"dev",
  "size":"124.03 GiB (133.18 GB)",
..
    "align":2097152,
    "devices":[
      {
        "chardev":"dax1.0",

# ndctl inject-error namespace1.0 -B 16 --count=1

# ./read_poison -x dax1.0 -o 8192 -m 1
Read poison location at (16 * 512 = 8192)

About a little under 30sec later, kernel panics.

thanks,
-jane