RDMA/core: Fix null-ptr-deref in ib_core_cleanup()

In the Linux kernel, the following vulnerability has been resolved:

RDMA/core: Fix null-ptr-deref in ib_core_cleanup()

KASAN reported a null-ptr-deref error:

KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f]

CPU: 1 PID: 379

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)

RIP: 0010:destroy_workqueue+0x2f/0x740

RSP: 0018:ffff888016137df8 EFLAGS: 00000202

...

Call Trace:

ib_core_cleanup+0xa/0xa1 [ib_core]

__do_sys_delete_module.constprop.0+0x34f/0x5b0

do_syscall_64+0x3a/0x90

entry_SYSCALL_64_after_hwframe+0x63/0xcd

RIP: 0033:0x7fa1a0d221b7

...

It is because the fail of roce_gid_mgmt_init() is ignored:

ib_core_init()

roce_gid_mgmt_init()

gid_cache_wq = alloc_ordered_workqueue # fail

...

ib_core_cleanup()

roce_gid_mgmt_cleanup()

destroy_workqueue(gid_cache_wq)

# destroy an unallocated wq

Fix this by catching the fail of roce_gid_mgmt_init() in ib_core_init().