[5.16.0-rc5][ppc][net] kernel oops when hotplug remove of vNIC interface

[Abdul Haleem]

Greeting's

Mainline kernel 5.16.0-rc5 panics when DLPAR ADD of vNIC device on my 
Powerpc LPAR

Perform below dlpar commands in a loop from linux OS

drmgr -r -c slot -s U9080.HEX.134C488-V1-C3 -w 5 -d 1
drmgr -a -c slot -s U9080.HEX.134C488-V1-C3 -w 5 -d 1

after 7th iteration, the kernel panics with below messages

console messages:
[102056] ibmvnic 30000003 env3: Sending CRQ: 801e000864000000 
0060000000000000
<intr> ibmvnic 30000003 env3: Handling CRQ: 809e000800000000 
0000000000000000
[102056] ibmvnic 30000003 env3: Disabling tx_scrq[0] irq
[102056] ibmvnic 30000003 env3: Disabling tx_scrq[1] irq
[102056] ibmvnic 30000003 env3: Disabling rx_scrq[0] irq
[102056] ibmvnic 30000003 env3: Disabling rx_scrq[1] irq
[102056] ibmvnic 30000003 env3: Disabling rx_scrq[2] irq
[102056] ibmvnic 30000003 env3: Disabling rx_scrq[3] irq
[102056] ibmvnic 30000003 env3: Disabling rx_scrq[4] irq
[102056] ibmvnic 30000003 env3: Disabling rx_scrq[5] irq
[102056] ibmvnic 30000003 env3: Disabling rx_scrq[6] irq
[102056] ibmvnic 30000003 env3: Disabling rx_scrq[7] irq
[102056] ibmvnic 30000003 env3: Replenished 8 pools
Kernel attempted to read user page (10) - exploit attempt? (uid: 0)
BUG: Kernel NULL pointer dereference on read at 0x00000010
Faulting instruction address: 0xc000000000a3c840
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
Modules linked in: bridge stp llc ib_core rpadlpar_io rpaphp nfnetlink 
tcp_diag udp_diag inet_diag unix_diag af_packet_diag netlink_diag 
bonding rfkill ibmvnic sunrpc pseries_rng xts vmx_crypto gf128mul 
sch_fq_codel binfmt_misc ip_tables ext4 mbcache jbd2 dm_service_time 
sd_mod t10_pi sg ibmvfc scsi_transport_fc ibmveth dm_multipath dm_mirror 
dm_region_hash dm_log dm_mod fuse
CPU: 9 PID: 102056 Comm: kworker/9:2 Kdump: loaded Not tainted 
5.16.0-rc5-autotest-g6441998e2e37 #1
Workqueue: events_long __ibmvnic_reset [ibmvnic]
NIP:  c000000000a3c840 LR: c0080000029b5378 CTR: c000000000a3c820
REGS: c0000000548e37e0 TRAP: 0300   Not tainted 
(5.16.0-rc5-autotest-g6441998e2e37)
MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 28248484  XER: 00000004
CFAR: c0080000029bdd24 DAR: 0000000000000010 DSISR: 40000000 IRQMASK: 0
GPR00: c0080000029b55d0 c0000000548e3a80 c0000000028f0200 0000000000000000
GPR04: c000000c7d1a7e00 fffffffffffffff6 0000000000000027 c000000c7d1a7e08
GPR08: 0000000000000023 0000000000000000 0000000000000010 c0080000029bdd10
GPR12: c000000000a3c820 c000000c7fca6680 0000000000000000 c000000133016bf8
GPR16: 00000000000003fe 0000000000001000 0000000000000002 0000000000000008
GPR20: c000000133016eb0 0000000000000000 0000000000000000 0000000000000003
GPR24: c000000133016000 c000000133017168 0000000020000000 c000000133016a00
GPR28: 0000000000000006 c000000133016a00 0000000000000001 c000000133016000
NIP [c000000000a3c840] napi_enable+0x20/0xc0
LR [c0080000029b5378] __ibmvnic_open+0xf0/0x430 [ibmvnic]
Call Trace:
[c0000000548e3a80] [0000000000000006] 0x6 (unreliable)
[c0000000548e3ab0] [c0080000029b55d0] __ibmvnic_open+0x348/0x430 [ibmvnic]
[c0000000548e3b40] [c0080000029bcc28] __ibmvnic_reset+0x500/0xdf0 [ibmvnic]
[c0000000548e3c60] [c000000000176228] process_one_work+0x288/0x570
[c0000000548e3d00] [c000000000176588] worker_thread+0x78/0x660
[c0000000548e3da0] [c0000000001822f0] kthread+0x1c0/0x1d0
[c0000000548e3e10] [c00000000000cf64] ret_from_kernel_thread+0x5c/0x64
Instruction dump:
7d2948f8 792307e0 4e800020 60000000 3c4c01eb 384239e0 f821ffd1 39430010
38a0fff6 e92d1100 f9210028 39200000 <e9030010> f9010020 60420000 e9210020
---[ end trace 5f8033b08fd27706 ]---
radix-mmu: Page sizes from device-tree:

the fault instruction points to

[root at ltcden11-lp1 boot]# gdb -batch 
vmlinuz-5.16.0-rc5-autotest-g6441998e2e37 -ex 'list *(0xc000000000a3c840)'
0xc000000000a3c840 is in napi_enable (net/core/dev.c:6966).
6961    void napi_enable(struct napi_struct *n)
6962    {
6963        unsigned long val, new;
6964
6965        do {
6966            val = READ_ONCE(n->state);
6967            BUG_ON(!test_bit(NAPI_STATE_SCHED, &val));
6968
6969            new = val & ~(NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC);
6970            if (n->dev->threaded && n->thread)

-- 
Regard's

Abdul Haleem
IBM Linux Technology Center