Re: Crash in indirect block infra after unloading driver module

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Jun 24, 2020 at 01:22:29PM +0300, Vlad Buslov wrote:
> Hi Pablo,
> 
> I've encountered a new issue with indirect offloads infrastructure. The
> issue is that on driver offload its indirect callbacks are not removed
> from blocks and any following offloads operations on block that has such
> callback in its offloads cb list causes call to unmapped address.
> 
> Steps to reproduce:
> 
> echo 1 >/sys/class/net/ens1f0/device/sriov_numvfs
> echo 0000:81:00.2 > /sys/bus/pci/drivers/mlx5_core/unbind
> devlink dev eswitch set pci/0000:81:00.0 mode switchdev
> 
> ip link add vxlan1 type vxlan dstport 4789 external
> ip addr add 192.168.1.1 dev ens1f0
> link set up dev ens1f0
> ip link set up dev ens1f0
> tc qdisc add dev vxlan1 ingress
> tc filter add dev vxlan1 protocol ip ingress flower enc_src_ip 192.168.1.2 enc_dst_ip 192.168.1.1 enc_key_id 42 enc_dst_port 4789 action tunnel_key unset action mirred egress redirect dev ens1f0_0
> tc -s filter show dev vxlan1 ingress
> 
> rmmod mlx5_ib
> rmmod mlx5_core
> tc -s filter show dev vxlan1 ingress

On module removal, the representors are gone and the ->cleanup
callback should be exercised, this callback removes the flow_block and
removes the rules in the driver.

Can you check if the ->cleanup callback is exercised?

> Resulting dmesg:
> 
> [  153.747853] BUG: unable to handle page fault for address: ffffffffc114cee0
> [  153.747975] #PF: supervisor instruction fetch in kernel mode
> [  153.748071] #PF: error_code(0x0010) - not-present page
> [  153.748189] PGD 5b6c12067 P4D 5b6c12067 PUD 5b6c14067 PMD 35b76b067 PTE 0
> [  153.748328] Oops: 0010 [#1] SMP KASAN PTI
> [  153.748403] CPU: 1 PID: 1909 Comm: tc Not tainted 5.8.0-rc1+ #1170
> [  153.748507] Hardware name: Supermicro SYS-2028TP-DECR/X10DRT-P, BIOS 2.0b 03/30/2017
> [  153.748638] RIP: 0010:0xffffffffc114cee0
> [  153.748709] Code: Bad RIP value.
> [  153.748767] RSP: 0018:ffff88834895ef00 EFLAGS: 00010246
> [  153.748858] RAX: 0000000000000000 RBX: ffff888330a30078 RCX: ffffffffb2da70ba
> [  153.748975] RDX: ffff888333635d80 RSI: ffff88834895efa0 RDI: 0000000000000002
> [  153.752948] RBP: 0000000000000002 R08: 0000000000000001 R09: ffffed106614600c
> [  153.759173] R10: ffff888330a3005f R11: ffffed106614600b R12: ffff88834895efa0
> [  153.765419] R13: 0000000000000000 R14: ffffffffc114cee0 R15: ffff8883470efe00
> [  153.771689] FS:  00007f6f6ac12480(0000) GS:ffff888362e40000(0000) knlGS:0000000000000000
> [  153.777983] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  153.784187] CR2: ffffffffc114ceb6 CR3: 000000035eb9e005 CR4: 00000000001606e0
> [  153.790567] Call Trace:
> [  153.796844]  ? tc_setup_cb_call+0xd8/0x170
> [  153.803164]  ? fl_hw_update_stats+0x117/0x280 [cls_flower]
> [  153.809516]  ? 0xffffffffc1328000
> [  153.815766]  ? _find_next_bit.constprop.0+0x3e/0xf0
> [  153.822079]  ? __nla_reserve+0x4c/0x60
[...]
> 
> I can come up with something to fix mlx5 but it looks like all other
> drivers that support indirect devices are also susceptible to similar
> issue.

How does the fix you have in mind look like?

Thanks.