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

From: Michael Ellerman <[email-masked]>
Date: Thu, 06 Jan 2022 15:19:15 +1100

Jakub Kicinski <[email-masked]> writes:
> On Wed, 5 Jan 2022 13:56:53 +0530 Abdul Haleem wrote:
>> 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@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);
>
> If n is NULL here that's gotta be a driver problem.

Definitely looks like it, the disassembly is:

  not     r9,r9
  clrldi  r3,r9,63
  blr				# end of previous function
  nop
  addis   r2,r12,491		# function entry
  addi    r2,r2,14816
  stdu    r1,-48(r1)		# stack frame creation
  li      r5,-10
  ld      r9,4352(r13)
  std     r9,40(r1)
  li      r9,0
  ld      r8,16(r3)		# load from r3 (n) + 16

The register dump shows that r3 is NULL, and it comes directly from the
caller. So we've been called with n = NULL.

cheers