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

From: Sukadev Bhattiprolu <[email-masked]>
Date: Thu, 6 Jan 2022 14:24:56 -0800

Michael Ellerman [[email-masked]] wrote:
> 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.

Yeah, Good catch Abdul.

I suspect its due to the release_resources() in __ibmvnic_open(). The
problem is hard to reproduce but we are testing following patch with
error injection. Will formally submit after testing/review.

---
From 8a78083e5ec6914be197352f391bfa17420a147c Mon Sep 17 00:00:00 2001
From: Sukadev Bhattiprolu <[email-masked]>
Date: Wed, 5 Jan 2022 16:22:58 -0500
Subject: [PATCH 1/1] ibmvnic: don't release napi in __ibmvnic_open()

If __ibmvnic_open() encounters an error such as when setting link state,
it calls release_resources() which frees the napi structures needlessly.
Instead, have __ibmvnic_open() only clean up the work it did so far (i.e.
disable napi and irqs) and leave the rest to the callers.

If caller of __ibmvnic_open() is ibmvnic_open(), it should release the
resources immediately. If the caller is do_reset() or do_hard_reset(),
they will release the resources on the next reset.

Reported-by: Abdul Haleem <[email-masked]>
Signed-off-by: Sukadev Bhattiprolu <[email-masked]>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 0bb3911dd014..34efba6c117b 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -110,6 +110,7 @@ static void ibmvnic_tx_scrq_clean_buffer(struct ibmvnic_adapter *adapter,
 					 struct ibmvnic_sub_crq_queue *tx_scrq);
 static void free_long_term_buff(struct ibmvnic_adapter *adapter,
 				struct ibmvnic_long_term_buff *ltb);
+static void ibmvnic_disable_irqs(struct ibmvnic_adapter *adapter);
 
 struct ibmvnic_stat {
 	char name[ETH_GSTRING_LEN];
@@ -1418,7 +1419,7 @@ static int __ibmvnic_open(struct net_device *netdev)
 	rc = set_link_state(adapter, IBMVNIC_LOGICAL_LNK_UP);
 	if (rc) {
 		ibmvnic_napi_disable(adapter);
-		release_resources(adapter);
+		ibmvnic_disable_irqs(adapter);
 		return rc;
 	}
 
@@ -1468,9 +1469,6 @@ static int ibmvnic_open(struct net_device *netdev)
 		rc = init_resources(adapter);
 		if (rc) {
 			netdev_err(netdev, "failed to initialize resources\n");
-			release_resources(adapter);
-			release_rx_pools(adapter);
-			release_tx_pools(adapter);
 			goto out;
 		}
 	}
@@ -1487,6 +1485,12 @@ static int ibmvnic_open(struct net_device *netdev)
 		adapter->state = VNIC_OPEN;
 		rc = 0;
 	}
+	if (rc) {
+		release_resources(adapter);
+		release_rx_pools(adapter);
+		release_tx_pools(adapter);
+	}
+
 	return rc;
 }
 
-- 
2.27.0

> cheers